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Vol. 15, No. 1, 2005, Nuclear Physics News 1

Editor: Gabriele-Elisabeth Körner

Editorial Board

J. D’Auria, Vancouver W. Kutschera, ViennaR. F. Casten, Yale M. Leino, JyväskyläT. W. Donnelly, MIT Cambridge R. Lovas, DebrecenA. Eiró, Lisbon S. Nagamiya, TsukubaM. Huyse, Leuven (Chairman) G. van der Steenhoven, Amsterdam

Editorial Office: Physikdepartment, E12, Technische Universitat München,85748 Garching, Germany, Tel: +49 89 2891 2293, +49 172 89 15011, Fax: +49 89 2891 2298,

E-mail: [email protected]

Nuclear

Physics

NewsVolume 15/No. 1

Nuclear Physics News is published on behalf of theNuclear Physics European Collaboration Commit-tee (NuPECC), an Expert Committee of the Euro-pean Science Foundation, with colleagues fromEurope, America, and Asia.

Correspondents

Argentina: O. Civitaresse, La Plata; Australia: A. W. Thomas, Adelaide; Austria: H. Oberhummer, Vienna; Belgium:

C. Angulo, Louvain-la-Neuve; Brasil: M. Hussein, São Paulo; Bulgaria: D. Balabanski, Sofia; Canada: J.-M. Poutissou,TRIUMF; K. Sharma, Manitoba; C. Svensson, Guelph; China: W. Zhan, Lanzhou; Croatia: R. Caplar, Zagreb; Czech

Republic: J. Kvasil, Prague; Slovak Republic: P. Povinec, Bratislava; Denmark: K. Riisager, Århus; Finland: M. Leino,Jyväskylä; France: G. De France, GANIL Caen; B. Blank, Bordeaux; M. Guidal, IPN Orsay; Germany: K. D. Gross, GSIDarmstadt; K. Kilian, Jülich; K. Lieb, Göttingen; Greece: E. Mavromatis, Athens; Hungary: B. M. Nyakó, Debrecen;India: D. K. Avasthi, New Delhi; Israel: N. Auerbach, Tel Aviv; Italy: E. Vercellin, Torino; M. Ripani, Genova; L. Corradi,Legnaro; D. Vinciguerra, Catania; Japan: T. Motobayashi, RIKEN; H. Toki, Osaka; Malta: G. Buttigieg, Kalkara; Mexico:

J. Hirsch, Mexico DF; Netherlands: G. Onderwater, KVI Groningen; T. Peitzmann, Utrecht; Norway: J. Vaagen, Bergen;Poland: T. Czosnyka, Warsaw; Portugal: M. Fernanda Silva, Sacavém; Romania: A. Raduta, Bucharest; Russia: Yu.Novikov, St. Petersburg; Spain: B. Rubio, Valencia; Sweden: P.-E. Tegner, Stockholm; Switzerland: C. Petitjean, PSIVilligen; United Kingdom: B. F. Fulton, York; D. Branford, Edinburgh; USA: R. Janssens, Argonne; Ch. E. Reece, JeffersonLab; B. Jacak, Stony Brook; B. Sherrill, Michigan State Univ.; H. G. Ritter, Lawrence Berkeley Laboratory; S. E. Vigdor,Indiana Univ.; G. Miller, Seattle.

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Nuclear

Physics

News

Volume 15/No. 1

Contents

Editorial .............................................................................................................................................................. 3

Letter to the Editor ............................................................................................................................................ 4

Laboratory Portrait

High Energy Accelerator Research Organization in Japan (KEK)by Shoji Nagamiya .......................................................................................................................................... 5

Feature Articles

Neutrino Physicsby Lothar Oberauer and Caren Hagner ....................................................................................................... 12

Structural Evolution in Nuclei: The Rich Structures of a Simple Hamiltonianby J. Jolie and R. F. Casten .......................................................................................................................... 20

Facilities and Methods

Application of Low Energy Spin Polarized Radioactive Ion Beams in Condensed Matter Researchby R. F. Kiefl, K. H. Chow, W. A. MacFarlane, G. D. Morris, C. D. P. Levy, and Z. Salman ...................... 26

Meeting Reports

Report on the 8th Nuclei in the Cosmos Conferenceby John M. D’Auria ...................................................................................................................................... 33

International Conference on Nuclear Data for Science and Technologyby Robert C. Haight and Mark B. Chadwick ................................................................................................ 34

News and Views ................................................................................................................................................ 36

Calendar ........................................................................................................................................................... 39

2 Nuclear Physics News, Vol. 15, No. 1, 2005

Cover illustration: A photo of High Energy Accelerator Research Organization in Japan (KEK) which is located on thefoothill of the Tsukuba Mountain. The largest ring at KEK is an electron-positron collider called the B-Factory. A smallring inside the B-Factory is the 12 GeV Proton Synchrotron, where nuclear physics activities are conducted. A ringadjacent to and outside the B-Factory ring is a photon factory with 2.5 GeV electrons (see article on page 5).

editorial


Be Ready: The International Year of Physics is Taking Off!

The views expressed here do not represent the views and policies of NuPECC except where explicitly identified.

It has been a long and hard waysince the European Physical Societyproposed in late 2000 to declare 2005as the “World Year of Physics” (WYP).This initiative has steadily madeprogress in its acceptance by theinternational organizations. The IUPAPendorsed it in October 2002, at itsGeneral Assembly in Berlin. TheGeneral Conference of UNESCO votedto accept it in Paris, in October 2003.Finally, in June 2004, in New York, theGeneral Assembly of the UnitedNations Organisation passed byacclamation a resolution declaring 2005as the “International Year of Physics”(IYP) (see: http://www.un.org/Depts/dhl/resguide/r58.htm and www.un.org/News/Press/docs/2004/ga10243.doc.htm.). At that point, one should recallthat only the UN General Assembly hasthe power to declare “International”years. So the “World Year of Physics”is now the “International Year ofPhysics”! The UN resolution on IYPhas been sponsored by the permanentdelegations of Brazil, France, Lesotho,Monaco, Portugal, Singapore, and theUnited Kingdom, and presented by theLesotho ambassador to the UN, Dr.Lebohang K. Moleko (see: http://www.un.org/webcast/ga.html). Dr.Moleko should be thanked for hisefforts to get the resolution passed.

In the meantime, physicists andPhysical Societies did not wait for thevote of the resolution at the UNassembly to start to plan and organizeevents, actions, exhibits, andconferences at the national andinternational level. Two WYP

preparatory meetings were held in Graz(July ’03) and Montreal (March ’04),in which many events plannedworldwide have been presented—seethe report on the Montreal meeting byChristophe Rossel, in EurophysicsNews 35 (3), p. 96, 2004. More recently,in October 2004, the European WYPcoordinators met in Mulhouse topresent their activity plans, to sharetheir experience, and to try to co-ordinate events between Europeancountries as much as possible. The levelof preparation of WYP activities wasfound to be quite advanced: museumexhibits for the general public aroundEinstein’s legacy and physical sciencesin general, radio and televisionprograms, commemorative coins andstamps, street events on physics themes,theatre plays, conferences, and so on.In Portugal, a coordinator in charge ofWYP relations and organization hasbeen officially accredited by thePortuguese government. Also, moreglobal activities, at the European leveland worldwide, are well on the way.These include activities such as“physics enlightens the world” (a relayof light signals around the globe),“physics talent search,” and “physicsas a cultural heritage” (a full accountof those global initiatives is given onthe Web page http://www.wyp2005.org). Funding for WYP activities is alsogrowing quickly both at the local andEuropean level: the EuropeanCommission has recently decided tosupport WYP activities in Europe byfunding, at the 2M€ level, via the“Science and Society” program, many

European organizations under theleadership of EPS.

The main objective of WYP 2005is to promote physics, to highlight itsimportance and impact in everyday life,and to remind us that physics is part ofhuman culture. Its main target is thegeneral public, and particularly youngpeople. This will be exemplified in the“kick-off” meeting of the InternationalYear of Physics, Physics for Tomorrow,which is being held at the UNESCOheadquarters in Paris, from 13–15January 2005. This conference, open tothe general public, aims at capturing theattention of the international press andmedia, so that events and celebrationsorganized around the world throughoutthe year will attract public and mediaattention. Half of those attending themeeting will be young students (500,with age ~16–21) coming from all overthe world, including developingcountries from Africa and Asia. Theywill have the opportunity to closelyinteract with prestigious speakers(among them several Nobel laureates)who will present their views on the roleof physics in society and in solving21st-century challenges (energy,environment, development…), on itstrans-disciplinary character and itsinfluence on other disciplines, on novelapproaches to physics teaching andscientific education, and so on.

As expected from an event thatopens a year where increasing thepublic awareness of physics andphysical sciences is a major goal, the“kick-off” conference will exhibitmarked features of general public

editorial


interest. This must be the rule for allthe events planned throughout the year2005, and one expects every physicistto accept his responsibility in thisrespect during the coming year, being

proactive in sharing his visions andconvictions about physics and sciencewith Society at large.

Happy and fruitful Year 2005!

MARTIAL DUCLOY

EPS Past-PresidentChair of the WYP International

Steering Committee

Letter to the Editor

In the article “Studies of ElementalSynthesis in Exploding Stars UsingDRAGON and TUDA withRadioactive Beams at ISAC,” NuclearPhysics News, vol. 14 no. 2, we claimthat “Until recently the technology hasnot been available to obtain requiredinformation on the rates of reactionsinvolving such short-nuclei species,with the exception of the firstmeasurement at the Louvain-la-Neuvefacility some years ago.” This statement

is clearly not correct. Unfortunately, theoriginal statement “Until recently thetechnology has not been available toobtain required information directly onthe rates of radiative capture reactionsinvolving such short-nuclei species,with the exception of the firstmeasurement at the Louvain-la-Neuvefacility some years ago,” somehow wasinadvertently changed. As was correctlypointed out to me by Carmen Anguloof Louvain-la-Neuve, the statement in

the article seemingly ignores theexcellent research using radioactivebeams that have been performed byvarious laboratories for about 15 years,for example, see review by M. S. Smithand K. E. Rehm, in Ann. Rev. of Nucl.Part. Sci. 51 (2001)91. This was not ourintent and we apologize to all on thismatter.

JOHN M. D’AURIA

AND LOTHAR BUCHMANN

laboratory portrait


High Energy Accelerator Research Organization

in Japan (KEK)

1. Introduction

In 1997 three institutions in Japan,National Institute for High EnergyPhysics (the original KEK), Institute ofNuclear Study (INS) at University ofTokyo, and Meson Science Laboratoryat Department of Physics of Universityof Tokyo, joined together to form a newinstitution called the High EnergyAccelerator Research Organization.The nickname of this new-borninstitution is called again the KEK.

The new KEK has two researchinstitutes: Institute of Particle andNuclear Studies (INPS) and Institute ofMaterials and Structure Science(IMSS). The main activity at INPS ishigh-energy physics, whereas an activenuclear physics research is alsoconducted at this INPS.

In nuclear physics research at KEKthree major areas are the highlights. Thefirst area is the research on theproperties of nuclear matter as viewedfrom quantum chromo dynamics(QCD). Experiments are in progress atthe 12 GeV Proton Synchrotron (12GeV PS). There, primary proton beamsas well as kaon beams are used. Inaddition, KEK supports nuclear matterphysics by funding a US–Japancollaboration program at BNL(PHENIX experiment).

The second area is nuclearspectroscopy, primarily hypernuclearspectroscopy with kaon- and pion-beams at the 12 GeV PS, and nuclearspectroscopy far from the stability lineby using a method of the targetfragmentation. Finally, the third area isneutrino physics by creating neutrinobeams at the 12 GeV PS and detectingthem at Superkamiokande (K2K

experiment).In addition, KEK is currently

promoting a new acceleratorconstruction, called the J-PARC, bycollaborating with Japan AtomicEnergy Research Institute (JAERI).

These activities are summarized inFigure 1, are they described in thisarticle.

2. The 12 GeV Proton Synchrotron

2.1. Hypernuclear PhysicsThe hypernucleus is a new type

nucleus for which a hyperon, Λ, Σ, andΞ, or two hyperons are embedded in anormal nucleus as an impurity, byhaving a new quantum number ofstrangeness. Because the hyperon doesnot obey a nucleonic Pauli principle, itcan be bound deeply inside the nucleus.

Namely, it probes a deep interior of thenucleus and, perhaps, modifies thestructure of the nucleus itself. Also, thenucleus might play as a micro-laboratory to investigate new nuclearforces, that is, the interactions betweenhyperon and nucleon, and even betweenhyperon and hyperon.

Hypernuclear physics programs atKEK-PS have been carried out withthree secondary beam lines of chargedpions and kaons: K6, K5, and K2.Although the beam intensities, the kaonintensity in particular, are not thehighest in the world, many interestingand important experiments have beenconducted by using a uniquespectrometer together with detectorsystems.

The Superconducting KaonSpectrometer (SKS) is a large

Figure 1. Summary of nuclear physics activities at KEK.

acceptance (100 msr) magneticspectrometer with a good energyresolution (2 MeV

FWHM), installed at the

K6 beam line. It has been used toproduce efficiently Λ hypernuclei withthe (Z+,K+) reactions. In the recentexperiments on non-mesonic weakdecay study of Λ

5He and Λ12C, successful

measurements were preformed to detectboth n-p and n-n pairs from Λp→np andΛn→nn processes, respectively. Itenabled us to determine branchingratios of these two decay modesunambiguously. Recently, doublecharge-exchange (Z-, K+) reactions wereutilized to produce Σs and neutron-richΛ hypernuclei for the first time.

A new detector system, called theHyperball Detector, was constructed forhypernuclear gamma-ray measure-ments. It consists of 14 germaniumdetectors, and it succeeded to measuregamma-ray transitions of Λ hypernucleiwith a few keV energy resolution. Withthis detector a new era of high precisionspectroscopy was open in thehypernuclear study. The first successfulmeasurement was performed togetherwith the SKS spectrometer for Λ

7Li; the

laboratory portrait

gamma-ray transition between theground state spin-spin doublet wasmeasured for the first time, as shownin Figure 2. Also, from themeasurement of E2 transition rate of anexcited state with Doppler-ShiftAttenuation method a nuclear shrinkageof ~19%, supposedly due to theexistence of a Λ hyperon inside the

nucleus, was observed [1].At K2 beam line, an experiment to

study the hypernuclei with strangeness–2 has been carried out by applying anemulsion-scintillating fiber hybridmethod. A new event that shows theproduction of ΛΛ

6He was clearlyobserved, as shown in Figure 3 [2]. Itunambiguously determines the mass ofthis double-Λ hypernucleus with Λ−Λinteraction energy of ∆BΛΛ = 1.01 ±0.20 + 0.18/–0.11 MeV. This value issmaller than the old value of about 4MeV estimated from the old emulsiondata in the 1960s. This event stimulateda large number of theorists and, as aresult, the importance of ΞN-ΛΛmixing effect has been pointed out.

2.2. K-Mesons in NucleiRecently, a tribaryon state,

S+(3140), was discovered in the neutronenergy spectrum from K- absorptionreaction on 4He target [3]. Furthermore,another strange tribaryon state,S0(3115), was measured in the protonspectrum [4]. The observed proton andneutron spectra are shown in Figure 4.

The aforementioned experimentalsearch was triggered originally by atheoretical work by Akaishi andYamazaki [5], which predicts theexistence of a deeply bound kaonic state(I = 0, Z = 1 and ~100 MeV in bindingenergy). However, the data cannot beunderstood well by this theory alone.

For example, the observed peak inthe neutron spectrum corresponds to thetheoretical prediction, whereas an evenlower-energy state, S0(3115) with I =1,Z = 0 and M

S0 ~ 3117 MeV/c2, is now

found in the proton spectrum. This massis even smaller than the mass of the I =0 state. In addition, the binding energyof kaon in both S0(3115) and S+(3140)is as large as twice of the theoreticallypredicted value.

Thus, the nature of the observed

Figure 2. A gamma-ray energy spectrum observed in KEK-PS E419 for the7Li(F+,K+γ) reaction.

Figure 3. A photograph of the emulsiontracks, showing the production of ΛΛ

6Heand its sequential weak decays.


laboratory portrait

states is still unclear. Nevertheless, theobserved large value of kaon bindingenergy is interesting. Furthermore, asindicated by the theory of Akaishi andYamazaki [5], this kaon might play arole as a catalyzer to induce theformation of an extremely high-densitysystem. If this is the case, a further studyof properties of kaon in nuclear matterfor a variety of nuclei is intriguing, inparticular, in terms of the study of a

restoration of chiral symmetry breakingfor a kaon in nuclear matter.

To pursue experimental researchtoward this direction, high-intensitykaon beams that can be provided by theJ-PARC (see later) would be needed.

2.3. Vector Mesons in NucleiIn the North Hall of the 12 GeV-PS,

there is a primary beam line called theEP1B. There, an experiment has beenperformed to measure lepton pairs fromvector mesons in nuclei. The purposeof these measurements is to study howthe meson gets buoyancy in the nucleus.

It is known that the mass of a barequark is light, whereas, once it is bound(confined) to form a meson or anucleon, it gains an additional mass.The aim of the present experiment wasto measure how the mass of a meson isdistorted if the meson is imbeddedinside the nucleus and, hopefully, tostudy the chiral properties of quarks innuclear matter.

A spectrometer was constructed tomeasure electron-positron pairs fromthe decays of ρ, ω, and φ mesons. InFigure 5, invariant mass spectra forthese pairs after subtracting backgroundare shown. A clear peak corresponds tothe mass of the ω meson.

An interesting observation is that atail is observed to the left of the peak in

excess of any calculations, and thisexcess cannot be interpreted by ourcommon knowledge. Perhaps, the tailcould be due that the mass of a ω and/or ρ mesons, which decay inside thenucleus, are distorted to a smaller valuethan the free ω meson mass.

Although further studies arerequired, the observed excess in theyield in the tail region is interesting

2.4. K2K Neutrino ExperimentIn 1998, a clear evidence for

neutrino oscillations was first reportedin the study of atmospheric neutrinosat the Super-Kamiokande [6]. Neutrinooscillation occurs among the threeknown flavors of neutrinos whenneutrinos carry non-zero mass andmixing.

The aim of the K2K experiment isto confirm the neutrino oscillationphenomenon, using muon-neutrinobeams produced by the 12 GeV PS. Thenear detectors at KEK measure theneutrino flux and energy spectrumimmediately after neutrino production,and thus, neutrino events beforeneutrino oscillation effects can bedetected. The beam was directedtoward the Super-Kamiokande detectorlocated 250 km away from KEK. Theenergy spectrum of the neutrino beamis similar to that of atmospheric

Figure 4. Missing mass spectraobtained by K- on 4He for proton(upper) and neutron (lower). The “ptrigger” requires an emission of acharged pion originated not from thereaction vertex but from opposite sideto the observed nucleon (solid circle).The triggered events show a clearexcess compared to slightly off-windowevents (open circle).

Figure 5. Observed invariant mass spectra of e+e- pairs from nuclear target.


neutrinos.Data-taking began in 1998. Data

analysis and understanding of detectorsystematics have been continuouslyimproved. After the analysis of the five-year data taken until May 2004, thefollowing results are obtained: (1) 107events have been observed at Super-Kamiokande, whereas the expectednumber is 151 (+12, –10) for no-oscillation hypothesis. (2) The observedneutrino spectrum reveals exactly thetype of distortion expected fromneutrino oscillation effects, as shownin Figure 6.

Based on these results, two pointsare concluded: (1) If there is nooscillation, the probability to detectonly 107 events and to obtain theobserved distortion in the energyspectrum is negligible (at the level of10-4). Namely, the neutrino carries afinite mass at the confidence level of99.99%. (2) K2K results are consistent

laboratory portrait

with those expected from theatmospheric neutrino oscillation resultspublished previously by Super-Kamiokande, which can only beattributed to the effects of neutrinooscillations.

3. J-PARC Project

3.1. Overview and ProgressSeveral years ago, KEK and the

Japan Atomic Energy ResearchInstitute (JAERI) started work on a jointventure to construct a new protonaccelerator at the highest beam powerin the world. The new accelerator is

targeted at a wide range of fields, usingK-meson beams, neutrino beams,neutron beams, and muon beams, tocover nuclear and particle physics,materials science, biology, and nuclearengineering, where these beams will becreated by bombarding high-powerproton beams on nuclei at rest. Theaccelerator is called the J-PARC, whichis an abbreviation of Japan ProtonAccelerator Research Complex.

Construction of the J-PARC facilitystarted in 2001 and the provision ofbeams is set to commence in the springof 2008. Construction work is currentlyin full swing in both areas of accelerator

Figure 6. Distortion of neutrino energyspectrum observed at Super-Kamiokande (data points). Labeled by“Without oscillation” representsexpectation in the absence of neutrinooscillations. Also shown is the expectedspectrum taking into account neutrinooscillation effects .

Figure 7. Artist’s impression of the completed J-PARC facilities (upper) and thecurrent status of construction (lower).


laboratory portrait

construction and civil engineering. Thephoto, shown in Figure 7, illustrates thepresent status of construction.

The accelerator complex, whichconsists of a linac, followed by asynchrotron to accelerate proton beamsup to 3 GeV. These beams will be sentto a laboratory for materials and lifescience with neutron and muon beams.Some of the proton beams from the 3GeV synchrotron ring will then be sentto another 50 GeV synchrotron ring.After being accelerated there, one beamwill be sent to the hadron experimentalfacility to produce primarily kaonbeams, with another beam being guidedtoward a neutrino beam line. Neutrinosare then measured using the SuperKamiokande detector 300 km away.

Because the performance of theaccelerator is largely determined at thefirst stage of the linear accelerator, thedevelopment of technology for thisportion is of crucial importance. Atthe beginning of November 2003, afull prescribed performance wassuccessfully attained.

J-PARC will be open to the wholeworld as an international facility. Thenumber of applicants from NorthAmerica and Europe in relation tonuclear and particle physics has alreadyexceeded the number of Japaneseresearchers. This project is expected toboost levels of participation from theAsia and Oceanic regions in neutronrelated fields. Work on the necessarypreparations to accommodate suchneeds is also going ahead in cooperationwith local governments includingTokai-mura Village and the IbarakiPrefecture.

In about 2010 it is anticipated thatJ-PARC will develop into one of theleading centers in the world. With thatdream in mind, the project team isworking day and night to forge aheadwith construction work. For those who

have interests in J-PARC, please visithttp://j-parc.jp/index.html.

3.2. Day-1 Experiments at J-PARCProposed nuclear physics

experiments at J-PARC are classifiedinto two categories: strangeness nuclearphysics and hadron physics. Theclassification is based on the differencein the beam requirements: The formerwill use secondary kaon beams inmedium energies of 1~2 GeV/c,whereas the latter will use either higherenergy secondary beams or the 50-GeVprimary proton beam. Most of theproposed experiments focus the quarkmany-body world from the viewpointof QCD.

In 2002, about 30 proposals weresent to the J-PARC Project Office. Apreliminary PAC was formed to discussthese proposals. Proposals are classifiedinto four categories. The first one is alarge-scale neutrino experiment, whichwill be described in the next subsection.The second is “Day-1 experiments” thatcan be started immediately after theturn-on of the beams at the HadronExperimental Facility. The third is“Phase-1 experiments” that can beplanned in the Hadron ExperimentalFacility while not ready on Day-1. Thefourth category requires a new beamline and a new experimental hall.

Concerning experiments related tothe fourth category, the J-PARC ProjectOffice decided to prepare a thirdextraction line from the 50 GeV PS,although no further considerations havebeen given at the present stage. Theneutrino program (the first category)was not on the budget table when theproposal was sent. Later, the budget forthis project was approved by theGovernment.

The Committee selected twoproposals for Day-1 at high priority.Both of them use kaon beams at 1.8 and

1.1 GeV/c. Emphasis of the firstproposal is to measure nuclear stateswith strangeness of S = –1 and –2. Thesecond Day-1 proposal sets a highpriority on the measurements of a kaonimplanted inside the nucleus. These twoexperiments are the natural extensionof the present experiments conductedat the 12 GeV PS at KEK, as describedin Sec. 2.1. and 2.2.

Finally, about 16 experiments forPhase-1 were proposed at the HadronExperimental Facility. Most of theproposals ask for kaon beams, whereasother beams such as high momentumprimary beams are also requested.

Because the first beam at the J-PARC will be available in 2008, anofficial call for the proposals will bemade soon, most likely within 2005.

3.3. T2K Neutrino ExperimentT2K (Tokai-to-Kamioka) experi-

ment is a next generation long baselineneutrino oscillation experiment, usingneutrino beams from J-PARC. Themuon neutrino beam produced by the50-GeV PS in J-PARC is directed to anddetected by the Super-Kamiokande at295 km from J-PARC. The intensity ofthe neutrino beam will be about 100times of the past K2K experiment at the12 GeV PS.

The main goals of the experimentare: (1) A discovery of an undetectedoscillation mode ν

µ→ν

e appearance,

and (2) a precise measurement of νµ

disappearance. Sensitivity of theunknown mixing sin22θ

13 is 0.006 (90%

CL), which improves the present upperlimit by about a factor of 20. As apossible future extension, a search forCP violation in the neutrino sector isenvisaged by multiplying the beampower and constructing a ~1 Mtonwater Cherenkov detector “Hyper-Kamiokande.”

The T2K experiment has been


approved by the Government in 2003and the construction started in April2004. The data taking will start in theearly 2009. International collaborationhas been formed. About 180 collabora-tors from 61 institutions in 12 countries(except students) signed up on the letterof intent as of August, 2004 [7].

R&D work including a design of thebeam line components has been inprogress at KEK, with closecooperation with participatinginstitutions in the T2K. Final design ofthe entire neutrino beam facility willfinish by March 2005. The constructionof the upstream portion of the decayvolume has been already started in2004. The design of neutrino detectorsin J-PARC site is also in progress.

4. Other Nuclear Physics Activities

4.1. TRIACThe TRIAC (Tokai Radioactive Ion

Accelerator Complex) facility is aradioactive nuclear beam (RNB)facility based on an isotope separatoron-line (ISOL) and a post accelerationsystem [8]. It has been constructed atthe Tandem facility in Tokai-site ofJAERI under the collaboration of KEKand JAERI. The facility consists of theISOL, an 18 GHz charge-breeding

laboratory portrait

electron cyclotron resonance ion-source(CB-ECR), and a linac complex, whichcomprises a split-coaxial RFQ(SCRFQ-) linac, an interdigital-H type(IH-) linac, and a superconducting(SC-) linac.

Primary protons as well as heavy-ions are supplied from 20 MV Tandemaccelerator, to produce radioactivenuclei via nuclear fusions, transfers, andfissions. For example, an expectedfission rate with 3 µA protons and UC-target is 1.5 × 1011 fissions/sec. Withthe aid of the CB-ECR, which is acharge state breeder for the massseparated singly charged ions, anefficient acceleration of the neutron-rich medium- or the medium-heavynuclide is available for studies invarious research fields, such as innuclear physics, nuclear astrophysics,nuclear chemistry, and materialsscience. Low-energy RNBs up to 1.1MeV/u are ready to use from the endof 2004 and more energetic RNBs from5 to 8 MeV/u will be also planned inthe near future by connecting the IH-linac to the SC-linac.

This facility will be open for usersfrom mid FY2005. Radioactive isotopes(102 types) in 18 elements have so farbeen extracted as mass separated RNBsfrom ISOL system in the beam

developments. For further informationof the TRIAC, refer to [8].

4.2. PHENIX Experiment at RHICQuarks are confined inside hadrons

and cannot be taken out as freeparticles. Lattice-QCD simulations,however, predicted the existence of anew phase of hadronic matter at hightemperatures, called the quark-gluonplasma (QGP). In this phase, quarksand gluons are liberated fromconfinement and move freely. It isbelieved that the QGP existed in theEarly Universe until ~10 µsecimmediately after the Big Bang. Recenttheoretical calculations have alsopredicted the existence of a liberatedquark soup at a high baryon densityregion, which may have relevance tothe inner core of the neutron star.

It is believed that a high-energyheavy-ion collision is a unique tool to

Figure 8. Overview of the T2K experiment.

Figure 9. Momentum spectra of neutralpions in p-p collisions (stars), and ascompared with those in Au-Au centralcollisions (closed circles) at c.m.s.energy of 200 GeV per nucleon pair.Yield in p-p collisions are scaled withthe number of binary collisionsobtained from the Glauber modelcalculation.


laboratory portrait

create high quark density matter, tostudy properties of an exotic quarkmatter in a laboratory. A new era towardthis direction began when theRelativistic Heavy Ion Collider (RHIC)[9] at Brookhaven National Laboratorystarted its operation in 2000. RHIC canprovide Au-Au head-on collisions at200 GeV per nucleon pair.

The Japanese group has beenparticipating in the PHENIXexperiment [10], under the US–Japancooperation program in the field of highenergy physics, funded by KEK. Thegroup consists of members from KEK,U. of Tsukuba, U. of Tokyo, WasedaU., Hiroshima U., and NagasakiInstitute of Applied Science. TheJapanese group constructed several keydetector subsystems in PHENIX, andthe group has been playing a leadingrole in executing experimental runs andanalyzing data.

Many interesting results have beenobtained [11]. One example is shownin Figure 9. It shows momentum spectraof neutral pions in both p-p collisionsand central Au-Au collisions, where theyield in p-p collisions is scaled with thenumber of binary collisions N

coll. The

Ncoll

scaling should hold in the zerothorder approximation for pionproduction in the high momentumregion. However, the observed result inthe high momentum region shows astrong hindrance in the yield for centralAu-Au collisions. After detailedstudies, it has been concluded that theobserved suppression in the high-momentum region is due to a creationof dense matter in Au-Au collisions,

and the hindrance is caused by anenergy loss of a parton (ancestor of apion) via strong interaction whilepassing through the matter.

4.3. Nuclear Theory GroupThe research that is currently in

progress by the nuclear theory group atKEK ranges from hadron physics toexotic nuclei including unstable nuclei,hypernuclei and kaonic nuclei.

Recently, new forms of hadron andhadronic matter have been the focusfrom both theoretical and experimentalsides. In the theory group a pentaquarkbaryon is studied in the QCD sum ruleand in the flux-tube model. New statesof the pentaquark baryon are alsopredicted. A new phase of quark matter,color ferromagnetic phase, is proposedas well. In addition, a theoreticalinvestigation of how the restoration ofchiral symmetry in hot matter affectson the observed spectrum of hadronshas been conducted.

Another highlight is that theexistence of deeply bound kaonic nucleihas been theoretically predicted, byshowing that the density is much higherthan the normal nuclear matter densityonce the kaon is bound inside thenucleus [5]. This might lead to a newform of cold and dense matter.

Energy levels and the structure ofhypernuclei have also been studiedsystematically, by using few-bodytechniques with the L-S coupling takeninto account.

For unstable nuclei, competition andcollaboration of the shell and clusterstructure have been clarified by the

method of Antisymmetrized MolecularDynamics.

Acknowledgments

This article was created fromcontributions from individuals who areeither KEK members or membersclosely related to KEK. They are: T.Nagae (Sec. 2-1 & 3-2), M Iwasaki(Sec. 2-2), H. En’yo (Sec. 2-3), K.Nishikawa (Sec. 2-4), T. Kobayashi(Sec. 3-3), H. Miyatake (Sec. 4-1), H.Hamagaki (Sec. 4-2), and O.Morimatsu (Sec. 4-3). Thanks go to allthese individuals.

References

1. K. Tanida et al., Phys. Rev. Lett. 86

(2001) 1982.2. H. Takahashi et al., Phys. Rev. Lett. 87

(2001) 212502.3. T. Suzuki et al., Phys. Lett. B 597 (2004)

263.4. M. Iwasaki et al., nucl-ph:0310018

submitted to PLB.5. Y. Akaishi and T. Yamazaki, Phys. Rev.

C 65 (2002) 044005.6. Y. Fukuda et al., Phys. Rev. Lett. 81

(1998) 1562.7. http://neutrino.kek.jp/jhfnu8. H. Miyatake and H. Ikezoe for the

TRIAC collaboration, Nucl. Phys.News, 14 (4), 37(2004).

9. RHIC home page: http://www.rhic.bnl.gov/.

10. PHENIX home page: http://www.phenix.bnl.gov/.

11. Most recent results can be found in theproceedings of Quark MatterConference, held in Jan. 2004: J. Phys.G 30 (2004) S633–S1430.

SHOJI NAGAMIYA

KEK


Neutrino Physics

LOTHAR OBERAUER

Technische Universität München

CAREN HAGNER

Universität Hamburg

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Introduction

It was a desperate attempt to rescueenergy and angular momentumconservation in beta decays whenWolfgang Pauli postulated the neutrinoin 1930. In his famous letter addressedto a meeting in Tübingen, Germany,Pauli expressed his apprehension thatthis new neutral and almost masslessparticle may never get detectedexperimentally. Indeed it took 26 yearsuntil F. Reines (Nobel prize 1995) andC. Cowan observed neutrinos via theinverse beta decay reaction ν–

e + p →

e+ + n which are emitted from thefission products in a nuclear powerreactor. Neutrinos only interact withmatter via weak forces and the crosssection was measured to be σ = (1.1 ±0.3) 10-43 cm2, which corresponds to anenormous absorption length of about29 light years! In 1957 parity violationin weak interaction was detected by C.Wu and only one year later the helicityof neutrinos by a famous experimentperformed by M. Goldhaber. He foundthe neutrino to be left handed, whereasthe anti-neutrino is right handed. Sincethe right handed partner of the neutrinois missing, neutrinos are massless in thestandard model. If the anti-neutrino isidentical to the neutrino it is calledMajorana particle.

It is known that neutrinos are alsoemitted in reactions where a muon isinvolved, for instance in the decay of apion: π+ → µ+ + νµ. But is that neutrinoνµ identical with ν

e? The decisive

experiment was performed at the AGSin Brookhaven by Ledermann,Schwartz, and Steinberger (Nobel prize1988) with a 15 GeV proton beam thatwas dumped in a Be-target producingpions and kaons that decay intoneutrinos. In a 15t spark chamber onlycharged muons were observed. Henceit was clear that νµ differ from ν

e. Today

we know that 3 families with 3 differenttypes of neutrinos exist. An indicationfor this fact was provided by the bigbang theory of cosmology. Directevidence for the existence of 3 neutrinoflavors was coming from the total widthof the Z0 resonance, measured at thelarge electron positron collider LEP atCERN, which was compared with thesum of all partial widths coming fromthe Z0-decay into hadrons and chargedleptons. The combined result from theLEP data was Nν = 3.00 ± 0.06. Directproof was finally provided in 2000 bythe DONUT experiment at Fermilabwhere the missing tau-neutrino wasdetected unambiguously byinvestigating neutrinos from the τ-decay of heavy charmed hadrons(Literature: F. Reines, Nobel LecturesPhysics 1991–1995, Ed. GöstaEkspong, World Scientific PublishingCo., 1997).

From Neutrino Masses to Neutrino

Oscillations

Today the question of neutrinomasses is focused. It has a fundamentalimpact on particle and astrophysics.

However, connected with neutrinomasses is the mixing of neutrino masseigenstates, which finally leads to thephenomenon of neutrino oscillations.

Fascinated by K0 ⇔ K

–0 oscillations

B. Pontecorvo in 1957–58 proposed asimilar phenomenon in the leptonsector: neutrino oscillations.

The present picture of neutrinooscillations arises from the fact that thethree flavor eigenstates v

e, v

µ, vτ are

linear combinations of the neutrinomass eigenstates v

1, v

2, v

3 (with masses

m1, m

2, m

3). The 3 × 3 complex, unitary

matrix U linking flavor and masseigenstates is called neutrino mixingmatrix (the lepton analogon to the CKMquark mixing matrix). Similar to thequark sector this matrix can beparametrized by three mixing anglesθ

12, θ

13, θ

23 and one CP-violating phase

δ. However if neutrinos are Majoranaparticles there could be two additionalCP-violating phases α

1 and α

2 .

Neutrino oscillations occur if aneutrino generated with a specificflavor propagates in space. It is a linearcombination of mass eigenstates, eachof which will propagate with a slightlydifferent frequency. At increasingdistances from the source the flavorcontent of the neutrino will change dueto the changing phase differencesbetween the mass eigenstates. Theseflavor transitions are called neutrinooscillations. In a simplified 2 flavorpicture the probability that a neutrinoof flavor α and energy E, traveling a


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distance L is detected as a neutrino offlavor β is given by

where θ is the mixing angle and ∆m2 =m

12 – m

22 is the squared mass difference

of the neutrinos. Neutrino oscillationexperiments can determine the mixingangles and squared mass differences.

If neutrinos propagate in matterresonant amplification of the oscillationscan occur due to the different types ofmatter interactions for different neutrinoflavors. This leads to effective mixingangles, which depend on the matterdensity. In current experiments thesematter effects play an essential role forsolar neutrinos (Literature: S. Bilenky,“Phenomenology of NeutrinoOscillations,” Prog. Part. Nucl. Phys.43:1–86, 1999).

Key Experiments I: Solar Neutrinos

and Reactor Experiments

The energy in the solar center isgenerated by thermonuclear fusion ofhydrogen to helium. The sum reactionis 4H + 2e– → 4He + 2ν

e and the energy

released hereby is ca. 26 MeV. Fromthe well-known solar luminosity S =8.5⋅1011 MeV cm-2s-1 one may estimatethe solar neutrino flux at Earth to be Φν≈ 2S / 26 MeV ≈ 6.5⋅1010 cm-2s-1.Quantitatively the fusion processesinside the sun are described in solarmodels. It is believed that in the sunthe so-called pp-cycle is the dominatingprocess. In the pioneering Homestakeneutrino experiment R. Davis provedthe basic idea of energy generation inthe sun. Deep underground theproduction of Ar-atoms in a 615t tankfilled with perchlorethylen (C

2Cl

4) has

been detected since 1970. They stemfrom the reaction ν

e + 37Cl → e– + 37Ar

and were extracted from the target tankafter an exposition of in average 60 to

70 days. The 37Ar atoms decay back viaelectron capture with a lifetime of ~50days. This decay was detected in smallproportional tubes. In average about 30Ar-decays were counted after eachextraction, proving the emission ofneutrinos in the sun. With thisexperiment the window for neutrinoastronomy has been opened. For hispioneering work R. Davis was honoredwith the Nobel prize in 2002.

However, there remained a puzzle.The measured neutrino rate wasroughly 1/3 of the expected one. As thethreshold for the reaction is rather high(814 keV) only a small part of theneutrinos emitted in the pp-cycle couldbe detected and it was argued that theobserved anomaly could be explainedby changing parameters of the solarmodel. Although many astrophysicistsdid not believe in this “solution” furtherexperimental data were desired.Since ca. 1990 two radiochemicalexperiments (GALLEX and SAGE)using the reaction ν

e + 71Ga → e– + 71Ge

measured the integral electron neutrinoflux at an energy threshold of 233 keV,which allows comprehension of allbranches of the solar pp-cycle. Bothexperiments are in perfect agreementand show a significant neutrino fluxdeficit of about 50%. In the meantimethe first direct detection of solarneutrinos with energies above ~7 MeVsucceeded in the Kamioka mine, Japan,via elastic neutrino electron scattering.The collaboration used a waterCherenkov detector where the directionof the neutrino could be measured.Again a clear deficit in the neutrino fluxwas observed. After the GALLEXresult it became evident that anastrophysical solution for the solarneutrino puzzle was excluded. On thecontrary neutrino properties beyond thestandard model of particle physics mustbe responsible for the disappearance of

solar neutrinos. Among severaldiscussed possibilities neutrinooscillation remained the most favorablescenario. The chase for the smokinggun of oscillation started. InSuperkamiokande, an upgraded waterCherenkov detector in Japan, thespectrum of high energy solar neutrinoswas measured with unprecedentedaccuracy. However, no deviation fromthe expected spectral shape wasdetected. The break through succeededwith the Canadian SNO (SudburyNeutrino Observatory) heavy waterdetector situated in the undergroundmine in Sudbury. In addition to neutrinoelectron scattering (es) two reactionscan be used ν

e + 2H → 2p + e– as well

as νx + 2H → p + n + ν

x. The former

charged current (cc) reaction can betriggered by ν

e’s only, whereas the latter

neutral current (nc) process is possiblefor all neutrino flavors. Therefore it ispossible to investigate whether solarneutrinos change the flavor on their wayfrom the sun to the earth. Theexperimental result is indeed exciting.The nc-reaction rate is significantlyexceeding the cc-reaction rate. From thedata one concludes that about 2/3 ofsolar neutrinos have changed theirflavor (Figure 1). This is a direct cluefor neutrino flavor transformation andimplies individual lepton numberviolation. The standard model ofparticle physics has to be extended.Interesting for astrophysics is themeasured nc-rate, which yields the totalsolar neutrino flux. It is in goodagreement with the rate predicted by thesolar model. Hence, we can concludethat the longstanding solar neutrinopuzzle is solved and neutrino flavortransition has been proven.

By analyzing the possible mass andmixing parameters it turned out that thebest fit values might be probed byterrestrial experiments, completely


independent from solar physics.Nuclear power reactors are a veryintensive source of low energy anti-electron neutrinos. Former searches foroscillations at reactors were performedat a distance of about 1 km at most andno hint for such an effect was found.However, at much further distances of~100 km or more the effect shouldappear if the flavor transition seen bythe solar experiments is really due toneutrino oscillations. The JapaneseKamLAND experiment in the Kamiokamine has measured reactor neutrinos atan average distance of about 180 kmwith a 1 kt liquid scintillation detectorsince the beginning of 2002. After morethan one year the first result wasreleased. The ratio of the observed rateto the expected one in case of nooscillations is r = 0.611 ± 0.085(stat) ±

0.041(syst). The probability to beconsistent with no oscillation is below5%. On the contrary, it is now evidentthat neutrino oscillations cause theflavor transition observed in solarneutrino experiments. This implies thatneutrinos mix and have mass. Veryrecently the KamLAND collaborationpublished new results with improvedstatistics. Now the energy spectrumshows a significant distortion that is inexcellent agreement with the spectralshape expected from neutrinooscillation (Figure 2).

The currently best global fit valuesare ∆m2

12 = 8.2+

-00

.

.65 × 10-5 eV2 for the

mass difference squared and tan2θ =0.40+

-00..0079 for the mixing angle. This is

the so-called Large Mixing Anglesolution for the solar neutrino puzzle.It describes the leading oscillations

between νe ↔ ν

µ. (Literature: J. Bahcall

and C. Pena-Garay, New Journal ofPhysics, 6, 2004, 63).

Key Experiments II: Atmospheric

Neutrinos and Accelerator

Experiments

Another evidence, actually the firstclaim of evidence for neutrinooscillations, came from the Super-Kamiokande (SK) collaboration, whoreported “Evidence for oscillation ofatmospheric neutrinos” in 1998.Atmospheric neutrinos are decayproducts of pions, kaons (and of thegenerated muons), which are producedin collisions of primary cosmic rayparticles with nuclei of the upperatmosphere. Therefore the ratio R ofmuon neutrinos to electron neutrinos isexpected to be R = (ν–

µ + ν

µ)/(ν–

e + ν

e)

≅ 2 independent of the energy. Theatmospheric neutrino problem had beenunder investigation since the 1980s byvarious experiments, for example, bythe water Cherenkov detectorsKamioka and IMB, who reportedR

measured / R

theory ≈ 0.6 and by the iron

calorimeters NUSEX and FREJUS whoobserved R

measured / R

theory ≈ 1.

The situation became clearer after1996 when the 50kton water cerenkovdetector Super-Kamiokande startedoperating and eventually collectedenough statistics to perform a zenithangle analysis of the observed electronneutrino and muon neutrino events (Inthe SK-I data set over 11000 events areused in the oscillation analysis). Thezenith angle is defined as the anglebetween the zenith direction and thedirection of the observed neutrino. Itturned out that although the number ofdownward muon events is as expected,the number of upward muon events isless than expected. The number ofelectron events both upward anddownward behaves as expected.

Figure 1. Evidence for flavor transformation of solar neutrinos in SNO. This plotshows the cc (red), nc (blue) and elastic scattering (green) neutrino fluxes (with1σ errors) measured by SNO as a function of the v

e-flux Φ

e and the v

µτ-flux Φµτ.

The slope of the blue band is -1 because ΦNC

= Φe + Φ

µτ. The blue band representsthe total 8B solar neutrino flux. The dashed lines indicates the value predicted bythe standard solar model. The red band is vertical because Φ

CCΦ

e. The slope of

the green band is given by the ratio of the ve and v

µ, vτ elastic scattering cross-

sections. Because all bands intersect in one point, consistent values for the ve and

the vµτ neutrino fluxes can be derived. One finds that Φ

µτ ≅ 2 ⋅ Φe. This means that

2/3 of the ve have transformed into v

µτ!

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Because the zenith angle of an eventcorresponds to the distance L of theneutrino traveled between its creationand detection, the oscillationprobability of a neutrino that dependson L will also depend on the zenithangle. The Super-Kamiokande zenithangle distributions for muon events arein excellent agreement with theneutrino oscillation hypothesis. Inprinciple one could have ν

µ → ν

e ,

νµ

→ ντ or νµ

→ νsterile

oscillations.However, ν

µ → ν

e oscillations in the

required parameter range are alreadyexcluded by the reactor neutrinodisappearance experiments CHOOZ

and Palo Verde. The sterile neutrinooscillation hypothesis can be tested,because one should observe fewerneutral current events for ν

sterile than for

νµ or ντ . In addition matter effects will

differ for sterile neutrinos. Based onthese facts, SK favors the ντ oscillationhypothesis. The best fit values are ∆m2

atm

= 2.1 × 10–3eV2 and sin2 2θatm

= 1.02and the allowed ranges at 90% C.L. are:1.5 × 10–3 < ∆m2

atm < 3.4 × 10–3eV2 and

sin2 2θatm

> 0.92.Recently, SK presented an analysis

with a restricted data sample,containing only events with very goodL/E resolution. For the first time the

typical oscillation pattern: a “dip” in theoscillation probability as a function ofL/E can be resolved and the exotichypothesis of neutrino decay anddecoherence can be excluded at the3.4σ and 3.8σ level.

The oscillation hypothesis foratmospheric neutrinos has beenconfirmed, yet with lower statisticalsignificance, by the final analysis of theMACRO and SOUDAN2 experiments.

In June 1995 K2K, the first longbaseline accelerator experiment startedwith the goal to test the oscillationhypothesis for atmospheric neutrinos.A beam consisting dominantly of ν

µ

with energies around 1 GeV is producedat the KEK accelerator facility in Japanand sent over a distance of 250 km tothe SK detector to count the number ofsurviving ν

µ. There is also a near

detector to determine the neutrino fluxand to study neutrino interactions. Ifone applies the oscillation hypothesiswith ∆m2

atm = 2 × 10–3eV2 and sin2 2θ

atm

= 1 to a muon neutrino of 1 GeV, theprobability to detect a muon neutrinoafter a distance of 250km is 0.7 (seesection 2). The SK collaboration reportsthat over 5 years of measurement, theywould have expected 151 muon events(no oscillation), whereas they actuallydetected 108 events. The best fit isobtained for an oscillation hypothesiswith ∆m2

atm = 2.7 × 10–3eV2, where sin2

2θatm

is assumed to be maximal. Inaddition the observed distortion in theenergy spectrum is also consistent withthe oscillation hypothesis. Using thetotal number of events and the spectralinformation, the K2K collaborationconfirms the neutrino oscillationhypothesis at 3.9σ.

At present there are three other longbaseline accelerator neutrino oscillationexperiments under construction: theMINOS experiment in the U.S. and theOPERA and ICARUS experiments in

Figure 2. Evidence for reactor anti neutrino disappearance and spectral distortionfrom KamLAND. This plot shows the prompt event energy (≈ E

v – 0.8 MeV) of the

ν–e candidate events. Because of various backgrounds, including a potential

contribution from geo-neutrinos below Epropmt

= 2.6 MeV, the reactor neutrinooscillation analysis was performed above this value. The best fit is obtained for∆m2

12 = 8.3 × 10–5eV2 and tan2θ = 0.41. This is in excellent agreement with the

oscillation parameters obtained from solar neutrino experiments! A global analysisfrom KamLAND and solar neutrino experiments yields ∆m2

12 = 8.2+

–00

.

.65 × 10–5eV2

and tan2θ = 0.40+–

00

.

.00

97 .

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Europe. The physics goal of theseexperiments is to further improve theprecision on ∆m2

atm (10%) and sin2 2θ

atm,

to prove the typical oscillation patternin L/E (MINOS) and to prove theappearance of ντ

(OPERA, ICARUS).All experiments will try to improve thepresent limit on θ

13 by searching for

subdominant νµ

→ ντ oscillations.These current experiments useconventional neutrino beams consistingdominantly of ν

µ, with a ~1%

background of νe. The CNGS (Cern to

Gran Sasso) beam has an energy abovethe τ production threshold in order toallow the identification of ντ bydetecting τ -decays. The NuMI(Fermilab to Soudan) beam is below theτ production threshold, because thislowers the backgrounds for the mainobjectives of the MINOS experiment.The MINOS experiment uses a near anda far detector. The latter is located inthe SOUDAN mine and consists of 5.4kton magnetized iron planes interleavedwith scintillator planes. The OPERAdetector provides a target of 1.8 ktonsof lead-emulsion bricks. The ICARUSdetector is a liquid argon TPC. A firstmodule will be installed with a targetof 0.6 ktons. The distance to the fardetectors is 730 km in all experiments.The far detector of MINOS is alreadyinstalled and running, takingatmospheric neutrino data. The NuMIneutrino beam will start by the end of2004. The CNGS neutrino beam isscheduled for 2006 and the OPERAdetector is presently being installed atGran Sasso (Literature: M. C.Gonzalez-Garcia et al., Phys. Rev. D63:033005, 2001).

Open Questions and Perspectives

The LSND Experiment and the Questionof Sterile Neutrinos

There is now compelling evidence

for neutrino oscillation from solar,atmospheric, reactor and acceleratorexperiments. All the experimentalresults are fully consistent with ∆m2

atm

= ∆m223

≅ ∆m213

= 2 × 10–3eV2 and ∆m2sol

= ∆m212

= 2 × 10–5eV2. However, thereis another claim of evidence forneutrino oscillation from the LSNDexperiment at Los Alamos, which doesnot fit in the simple picture of threemassive neutrinos. LSND reportsevidence for ν–

µ → ν–

e oscillation with

∆m2LSND

≅ 1eV2. In order to explain thisthird mass difference one would haveto introduce a fourth neutrino. Becausethe number of active neutrino flavorsis measured to be 3, the fourth neutrinowould have to be a so-called sterileneutrino. The goal of the MiniBooNEexperiment at Fermilab, which startedin 2002, is to test the LSND claim. Atpresent MiniBooNE has collected 28%of the necessary data and expects firstresults in 2005.

Direct Searches for Neutrino MassesAlthough we know the neutrino

mass differences from neutrinooscillation experiments the absolutemass levels are still unknown. Forcosmology the absolute masses ofneutrinos are extremely important. Ifthe level for the masses would be~10 eV, neutrinos would significantlycontribute to the energy density of theuniverse.

The most sensitive test for absoluteneutrino masses comes from precisemeasurements of the tritium beta decayspectrum. A finite neutrino mass wouldbe detected by a deviation of thespectral shape close to the endpoint.Today the best limits are provided bytwo experiments, performed in Troitsk,Russia, and Mainz, Germany. In bothexperiments a large retarding magneticsolenoid is used. The spectrometer hasa large acceptance as the transverse

momentum of an emitted electron istransferred to the longitudinal directionby the inhomogeneous magnetic field.No significant deviation from theexpected spectrum has been found andthe quoted limits are at 2.2 eV. As weknow the mass differences to be muchsmaller, one can set an upper limit onthe sum of all flavors (i.e., ∑mν (i) <6.6 eV) and hence constrain thecosmological energy density due toneutrinos.

In a future experiment, KATRIN atKarlsruhe, Germany, the sensitivityshould be increased by one order ofmagnitude. This is an important goalas the neutrino mass still has importantlinks to the developments of largestructures, of r-processes inSupernovae, and perhaps even with thequestion of the origin of ultra highenergy cosmic rays.

Searches on neutrinoless doublebeta decays (ββ–0ν) test absoluteneutrino masses too. Besides also thenature of neutrinos is probed. Only ifneutrinos are Majorana particles, ββ–0ν decay may occur. This processviolates Lepton number conservation.Additionally a flip of the chirality isnecessary. This can be provided by afinite neutrino mass. The amplitude ofthis process is proportional to m2

ββ =|∑U2

eim

i|2, the squared sum of all mass

eigenvalues weighted with the mixingprobabilities. There exist several gg-nuclei which are candidates for ββ–0νdecays. Experimentally the betaspectrum is investigated. Besides thecontinuous spectrum due to the allowedββ–decay with emission of twoneutrinos a mono-energetic line shouldappear at the endpoint if ββ–0ν decayoccurs. The currently best limit comesfrom the Heidelberg-Moscowexperiment, performed at the Gran-Sasso underground laboratory in Italywith 5 Ge-detectors using in total

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10.9 kg of enriched 76Ge (86%). Theobtained lifetime limit T

1/2 = 1.9·1025 y

corresponds to a mass limit of mββ <0.35 eV (90% CL). Performing a newpeak analysis a part of the collaborationhas published evidence of a line veryclose at the endpoint of 2039 eV.Interpreting this line as due to ββ–0νdecay would imply mββ < (0.1–0.9) eV.The large uncertainty is mainly causedby the lack of knowledge about thenuclear matrix elements. Whether thispeak is due to new physics or simplyan unidentified background line is notclear yet. If confirmed in future Ge-experiments (GERDA in Europe,Majorana in the USA), the effect shouldbe probed with other isotopes. Oneexample is Cuoricino at Gran-Sasso, anexperiment using 42 kg of TeO

2 as

cryogenic detector. The candidate 130Tehas a higher endpoint (2.6MeV), whichis advantageous due to the larger phasespace and the lower background. Otherprojects using 136Xe or 150Nd (endpoint3.2 MeV) are in the R&D phase.Generally, future projects aim to reachsensitivities of ~20meV for mββ(Literature: Y. Grossmann, TASI 2002Lectures on Neutrinos, hep-ph/0305245. H.V. Klapdor-Kleingrothaus,“Sixty Years of Double Beta Decay,”World Scientific 2001 and NIM A, Vol.510, No. 3, 2003, 281).

Θ13

and CP-ViolationTwo of three mixing angles of the

neutrino mixing matrix have beenmeasured. Both are relatively large.

It should also be pointed out that thelarge values of two neutrino mixingangles are in contrast to the stronghierarchy of the CKM mixing anglesin the quark sector of the standardmodel. The only mixing angle, whichremains to be determined is θ

13. The

best limit sin2 2θ13

> 0.2 at 90%CL (for∆m2

13 = 2·10–3eV2) was obtained in the

CHOOZ reactor neutrino experiment,where no disappearance of ν–

e was

observed at 1km from the reactor core.The size of the missing mixing angleθ

13 would be another important

indicator for the correct neutrino massmodel and the new physics behind it.Therefore great efforts are presentlyundertaken in order to design and buildexperiments optimized for sensitivityon θ

13. One uses the fact that θ

13 will

cause small subdominant effects in thethree flavor oscillation probabilitiesmeasured at L and E values, whereoscillations due to ∆m2

atm are dominant

There are two oscillation channels inwhich one can observe these effects.The first is νµ → ν

e oscillation, where

the probability depends not only on θ13

,but also on the two mass differences,all mixing angles and the CP-violatingDirac phase δ. This offers the advantagethat δ is in principle detectable.However, correlations and degeneracieswill require more than one experimentin order to disentangle the values of allunknown parameters. This method willbe used in neutrino superbeamexperiments. The second channel, usedby reactor experiments, is ν–

e → ν–

e

where the probability to measure thedisappearance of anti electron neutrinosis proportional to sin2 2θ

13 and strictly

independent of δ. Therefore one willobtain a clean value for θ

13.

Superbeam experiments are plannedin the U.S. at Fermilab (NOVA) and inJapan at the J-PARC facility (T2K).Superbeams are produced likeconventional neutrino beams, but theproton beam power will be muchincreased (in the MW range). In bothexperiments the detectors will belocated off-axis with respect to thebeam. It turns out that by varying theoff-axis angle, the average neutrinoenergy in the beam can be tuned to theoptimal value, which maximizes νµ →

ντ oscillations at the given long baselinedistance (~800km for NOVA and295km for T2K). In addition the energyspectrum becomes very narrow, whichreduces the background. The detectorfor the Japanese experiment will be thewater cerenkov SK, the J-PARC facilityis already under construction. TheNOVA detector will be a large (~50kton) calorimeter, with scintillatorplanes. With this experiment, neutrinophysics will be back above ground, asthe detector no longer requires to beunderground due to the short beampulses. Baseline distance and neutrinoenergies are different in the twoexperiments, which might allow todisentangle some of the degeneraciesand correlations. The superbeamexperiments will start around 2009.

Reactor experiments have beendiscussed intensively in the last twoyears, since the clean information onθ

13 would help to resolve the mentioned

correlations and degeneracies. In order

to improve the CHOOZ limit, one hasto increase statistics and to reduce thesystematic errors to the 1% level. Thisis possible by comparing the rates andenergy spectra of a near detector (atdistances of 100–200 m) to those of afar detector (at distances 1–2 km). Bothdetectors should have at least 10 tonsof active target. The target is typicallya Gd loaded liquid scintillator providinghigh neutron detection efficiency. Agood candidate is the Double-CHOOZexperiment at the old CHOOZ site inFrance, where one could use again theexisting underground far detector site.The first precision reactor experimentscould start around 2008 and will be ableto reach sensitivities of the ordersin2 2θ

13 < 0.03. This could be further

improved in future larger experiments.In the far future (~2015) it is

planned to increase the detector size andbeam intensity for the superbeam

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experiments. This second generation ofsuperbeam experiments will have thegoal to determine the CP-violatingDirac phase, which is however onlypossible if the size of θ

13 is not too

small. The priority for the presentgeneration of experiments is thereforeto determine θ

13.

The ultimate high energy neutrinosource could be a neutrino factoryproviding pure ν

e, ν

µ (and anti neutrino)

beams. Recently the concept of so-called beta beams became veryattractive and feasibility studies areunder way. Radioactive ions (goodcandidates are 6He and 18Ne), which candecay in β+ or β- mode and thus emit ν

e

and ν–e, are accelerated to energies

around 150 GeV/nucleon. They arethen stored in bunches in a storage ring.The novel features of these beams arethat they contain exactly one flavor, theenergy spectrum is very well knownand the collimation is very good.Possible sites include CERN, GSI, andGANIL (Literature: P. Huber et al.,“Prospects of accelerator and reactorneutrino oscillation experiments for thecoming ten years,” hep-ph/0403068).

Neutrinos in Astrophysics andCosmology

Solar neutrino physics opened thewindow to astrophysical observationswhere neutrinos are used as probes.Indeed the basic idea of thermal nuclearfusion as source for stellar energies wasproven by detecting solar neutrinos andin future important details about the pp-and the CNO-cycle may be revealed bynew experiments in this field. The firstneutrino signal outside of our solarsystem, even outside from our galaxywas observed in February 1987 when ablue giant star in the Large MagellanicCloud exploded as a supernova at adistance of about 50 kpc (ca. 150 lightyears). In total 19 neutrino events were

recorded in two large water Cherenkovdetectors (Kamioka, Japan, and IBM,USA) within a time window of about20 seconds. This observation allowedus to measure for the first time theenergy release of a gravitationalcollapse, as about 99% of the totalgravitational energy is emitted inneutrinos. In spite of the small numberof events the basic idea about themechanism of a supernova of thisnature (i.e., SN type II) was confirmed.With running detectors, like SuperKamiokande, a supernova type IIexplosion in our galaxy would beaccompanied by a neutrino signal ofabout 15,000 events within ~20seconds. Hence, the development of agravitational collapse could be followedin great detail. In order to measureflavor dependent fluxes different nucleias target for neutrino are proposed. InLENA (Low Energy neutrinoAstronomy) a large liquid scintillatordetector is proposed to serve as detectorfor supernova neutrinos. Here neutrinointeractions on protons as well as on12C could be used that would allow usto disentangle the flavor compositionof a supernova burst in time and energy.From all past supernova type IIexplosions in our universe one expectsa low background of relic supernovaneutrinos. Up to now only upper limitson the flux of those SNR-neutrinos arereported. In LENA or in a modifiedSuperKamiokande detector (Gd-loadedwater) the detection of SNR-ν’s couldsucceed and would tell us details aboutstar formation in the early universe.

Neutrinos should have been emittedin an enormous number in the big bang.After ~1 second neutrinos decoupledfrom matter and since then they are freestreaming in the universe. Due to theexpansion of the universe they are red-shifted and their mean temperatureshould be 1.95 K, a little lower as the

cosmic microwave background (CMB).Up to now this extreme low energyneutrino flux could not be detected. Bigbang nucleosynthesis sets limits on thenumber of neutrino flavors and neutrinomasses. Even better limits are comingfrom recent redshift surveys andmeasurements of the CMB. Thereported limits on the neutrino mass aresomehow model dependent and are inthe range between 0.7 eV and 1.8 eV. Itis amazing that this cosmological limitsare in the same range as laboratoryconstraints or even slightly better. Onthe other side neutrino oscillations seta lower limit on the neutrino mass.Therefore we know that neutrinoscontribute to the mass density of theuniverse. They are the first detected hotdark matter particles. Their density Ωνin unit of the critical density is restrictedto 0.001< Ων < 0.04.

Geophysical neutrinos may tell usabout the concentrations of U, Th, andK in the Earth. The contribution ofterrestrial radioactivity to the energyflux from the Earth (in total about 30TW) is still unknown. With large liquidscintillation detectors like KamLAND,Borexino, and LENA the U- and Th-concentrations could be measured atdifferent sites. Therefore it could bepossible to disentangle thecontributions from the continental andoceanic crusts. With LENA is shouldbe even possible to determine theconcentrations in the mantle of theEarth.

Some geophysicists believe that agigantic natural nuclear reactor at thecenter of the Earth provides the energyfor the Earth’s magnetic field. Thisappearing wild hypothesis can be testedby a future low energy neutrino detectoras proposed e.g. in LENA.

High energy neutrinos may act asprobes from astrophysical objects likesupernova remnants, binary systems,

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active galactic nuclei, and quasars. Theneutrino source could be high energypions and kaons which decay in flight.Large Cherenkov detectors under waterand in ice are going to be constructedto detect those neutrinos. At the southpole the Amanda detector is alreadytaking data and the 1 km3 large Icecubeproject is under way. High energyneutrinos are detected via chargedcurrent interactions by measuring thegenerated charged leptons. As there isa large background from atmosphericmuons only upgoing particles can beused as neutrino candidates. Hence,Amanada and Icecube will probe thenorthern hemispere of the sky for pointlike neutrino sources. In order to coveralso the southern part a largeunderwater detector is discussedfor the Mediterranean Sea. Threecollaborations (Antares, Nestor, Nemo)are exploring the best site for the finalexperiment that should start taking dataat about 2008. High energy cosmicneutrinos may also generate airshowers. In the Auger experiment inMendoza, Argentina, the air shower aswell as fluorescence of N

2 in the

atmosphere should be observed. Theformer is detected by a large numberof water Cherenkov detectors, the latterby phototubes in the form of a fly’s eye.In total 2 arrays with 3000 km2 areaeach should be covered. The secondarray should be constructed in thenorthern hemisphere to cover the wholesky. With Auger even events withenergies above ~1020 eV will bedetected. The full deployment inArgentina is expected for the year 2005(Literature: L. Oberauer, ModernPhysics Letters A, Vol. 19, No. 5, 2004,1–12. T. Gaisser, F. Halzen and T.Stanev, “Particle Astrophysics withHigh Energy Neutrinos,” Phys. Rept.258:173–236, 1995).

Conclusion and Outlook

In 2005 we will celebrate the 75thanniversary of Paulis neutrino postulatein Tübingen. Since then neutrinophysics has evolved into a key domainof particle physics, where we expect tofind hints leading to new physics at highenergy scales and grand unification. In75 years impressive experimentalresults have been achieved, culminating

in the recent past with the discovery ofneutrino oscillation. The window toneutrino mass and mixing is open! Thefirst precision measurements of massdifferences and mixing angles havestarted and many will follow. Butalthough many of the neutrinoparameters are now known, some stillhave to be determined until our pictureof the neutrino sector is complete. Themost important questions are: What isthe mass of the lightest neutrino andwhat is the mass hierarchy? Areneutrinos Majorana particles? What isthe value of θ

13? Is there CP-violation

in the lepton sector? Although there ishope that these questions might beanswered with the present or nextgeneration of experiments, for some ofthem it might take decades again.

On the other hand detectortechnology and our knowledge ofneutrinos have already so muchimproved that it is now possible to useneutrinos as probes, for example, inastrophysics. Therefore in the nextyears we are awaiting many interestingand maybe surprising results fromneutrino physics.

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Web-Calendar of Nuclear Physics Events, Conferences, Workshopsand Schools, Meetings of Large Collaborations, PAC meetings, etc.

Available through the NuPECC website: www.nupecc.org

Add your event by contactingGabriele-Elisabeth Körner ([email protected])

To make the Nuclear Physics News calendar even more useful it is now being put on the Web and is expanded toinclude other nuclear physics events than just conferences. Many of us have had two different meetings to attend at thesame time: the first step toward avoiding this is to have information easily available on what is going on in ourcommunity. To achieve this, please help us to keep the calendar updated: make sure that all conferences, all collaborations,and all laboratories send information to us.

KARSTEN RIISAGER, Aarhus UniversityGABRIELE – ELISABETH KÖRNER, NuPECC

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Structural Evolution in Nuclei: The Rich Structures

of a Simple Hamiltonian

J. JOLIE

Institute for Nuclear Physics, University of Cologne, Zulpicher Str. 77, D-50937 Cologne, Germany

R. F. CASTEN

Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06520, USA

Introduction

One of the most interestingdevelopments in low energy nuclearstructure in recent years is a newperspective on structural and shapeevolution, as a function of N and Z.Much of this renewed interest hasbeen generated by discoveries ofphase transitional behavior at lowenergies in finite nuclei and theproposal and validation of the ideaof critical point symmetries. Beyondthis, the subject embraces the conceptsof dynamical symmetries, Landautheory, a new mapping of structuraltrajectories for a wide variety ofnuclei, and order and chaos in nuclearspectra. In this short overview, we willfocus on even–even nuclei althoughfascinating applications to odd–evennuclei, exploiting the concept ofnuclear supersymmetry, have recentlybeen made. We will frame ourdiscussion in the context of the richstructures of a simple Hamiltonian ofIsing form [1].

Collective Structures and

Structural Evolution

We will focus our discussion oncollective nuclei, which can have arange of structures from spherical todeformed (axially symmetric, prolate oroblate, or with various degrees of γ-softness). Consider the followingschematic Hamiltonian

H = aHsph

– bHdef

(1)

It is of Ising form, exhibiting acompetition between equilibriumconfigurations of two differentsymmetries: the first term is sphericaldriving, the second deformationdriving. For small b/a the equilibriumsolution is spherical, but a deformedconfiguration can co-exist at higherenergies (see Figure 1, curves 1, 2). Asb/a grows, the deformed solutiondescends in energy and, for some b/a(curve 3 in Figure 1), crosses thespherical one to become the groundstate. This is the first order phasetransition where the deformation, β,jumps discontinuously from 0 to finiteβ. Thereafter, for larger b/a, theequilibrium solution remains deformed(curves 4, 5).

We can write a Hamiltonian like thatof Eq. (1) in the context of the IBAmodel [2] using the simple ConsistentQ Formalism as follows

H = α(ηnd –

1–η QχQχ) (2)

where N is the boson number. Here wehave used η to play the role of a/b andpulled out an overall energy scalingfactor α. Eq. (2) is written so that thefull range of structure is described byη values in the range of 0 to 1. The firstterm is diagonal in the number of s andd bosons of the IBA, and gives energies

that scale as the d–boson number. Ittherefore gives a set of equally spacedsolutions corresponding to a sphericalvibrator; the second term, which is aquadrupole interaction between bosons,mixes the s and d boson basis states ofthe IBA, and yields deformed solutions.The equilibrium shape is spherical forη values ranging down from unity,crosses from spherical to deformed atsome value of η ≡ η

crit, and is deformed

for η < ηcrit

. The form of the quadrupoleoperator introduces another parameterχ, which is related to axial asymmetry,and which notably increases therichness of the structures possible with

N

Figure 1. Energy surfaces of asequence of nuclei evolving fromspherical to deformed in a first orderphase transition with changes innucleon number. Curve 3 correspondsto the phase transition where theequilibrium value of the deformation,β, changes discontinuously.

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Eq. (1). The parameter χ ∈ [- 7/2, 7/2]: χ

= - 7/2 (+ 7/2) corresponds

(if η < ηcrit

) to a prolate (oblate) axiallysymmetric rotor and χ = 0 to acompletely γ-soft rotor.

In order to visualize this simpleparameterization the Casten triangle isused in which any position is definedby η and χ. Such a triangle is shown inFigure 2. The great interest of thesimple Hamiltonian of Eq. (2) lies inthe fact that it can be used to locate mostnuclei in the triangle and that one canvisualize the general six-dimensionalIBM Hamiltonian in a two-dimensionalimage. Moreover the triangle isconstructed such that the three cornersare formed by the three dynamicallimits of the IBM: U(5) (η = 1), O(6)(η = 0, χ = 0), SU(3) (η = 0, χ =-

7/2). These limits describe vibra-

tional, γ-unstable, and prolate deformednuclei. Figure 2 contains mini levelschemes illustrating some keyobservables showing the characteristiclevel and transition rate patterns for

each dynamical symmetry. Thesesymmetries have been discussed earlierin NPNI [3]. One notices that, althoughthe number of parameters is reduced totwo, the Hamiltonian contains the richgroup structure of the IBM.

To understand the evolution ofstructure with (η, χ) it is useful to turnto the classic Landau theory [4] of phasetransitions. This will also allow ageneralization of the triangle [5]. To dothis, we note that the IBA Hamiltonianof Eq. (2) can be written in terms of theshape variables β and γ, using anapproach called the coherent stateformalism. The details are notimportant: the main point is that theenergy surface can be written as anexpansion of the nuclear energyfunctional in powers of β:

Φ=Φ0+Aβ2+Bβ3cos3γ+Cβ4+O(β5) (3)

where Φ0 corresponds to a spherical

solution. Equilibrium conditions occurwhen Φ is a minimum for some value(s)

of β0 and γ

0. If such a minimum occurs

at β0 = 0 one has the higher (spherical)

symmetry and for β0 ≠ 0, the lower

(deformed) symmetry. A, B, C . . . areparametric functions of some controlvariables. In classic Landau theory, theyare often pressure and temperature. Inthe nuclear case, they would depend,for example, on the number ofnucleons, the orbits they occupy, andthe interactions of these nucleons,which we parameterize in terms of ηand χ.

We now present a simplifiedanalysis, which largely ignores theparameter γ, because its influence istrivial. We keep terms up through theβ4 term in Eq. (3). The equilibriumvalues are either γ

0 = 0o when B < 0, or

γ0 = 60o when B > 0. The linear

dependence on B then allows one toabsorb the influence on γ in the sign ofB. This analysis, although over-simplified, captures the essence of thephysics.

For any stable equilibrium state, thefirst derivative of Φ with respect to βmust be zero and the second derivativepositive. Thus, one obtains:

β(2A+3Bβcos3γ +4Cβ2) = 0 (4)

and

2A+6Bβcos3γ +12Cβ2 > 0 (5)

First of all, C should be positive toget finite solutions. This gives twosolutions. One is the spherical solution(β

0 = 0), which, from Eq. (5), implies

A > 0. This is reasonable. The sphericalequilibrium solution of Eq. (3) (β

0 = 0)

is only possible if Φ has a minima atβ = 0 that requires A > 0. The secondsolution corresponds to β

0 ≠ 0. This

solution is obtained by solving thequadratic in Eq. (4). For the moment,consider the case where B = 0 in Eq.(3) (a line in A - C parameter space).

Figure 2. Symmetry triangle of the IBA model. The dynamical symmetries areindicated at the vertices, along with mini-level schemes showing theircharacteristic properties. The numbers on the transition arrows are relative B(E2)values in the limit of large N. The physical meaning of the parameters η and χ indefining positions within the triangle are also identified.

This is illustrated in Figure 3 (left).Then, trivially,

β0 = ±

–A(6)

For finite and real β0 this requires A and

C to be of opposite sign. Since, forsmall β, the β2 term dominates, one hasa deformed minima only when Φ in Eq.(3) initially decreases as β increasesfrom zero, which requires A < 0. Theminimum is produced when the β4 termdominates.

Thus, we see that the nuclear phasediagram has three phases, spherical(β

0 = 0), prolate (β

0 > 0), and oblate

(β0 < 0). The spherical–deformed phase

transition occurs when A changes frompositive to negative, that is, at A = 0.Spectra corresponding to simplemodels of these cases have beendiscussed recently in NPNI [6]. Theprolate–oblate phase transition occurswhen B changes from negative topositive, that is, it occurs at B

= 0 (and

A < 0, C >

0). As illustrated in Figure 3

(left), if we think in terms of a η, χphase diagram analogous to the P, Tdiagram of Landau theory, then the firstorder phase transition conditions, A

= 0

or B = 0, each corresponds to a curve in

the phase diagram. These two first orderphase transition trajectories meet at anisolated second order phase transition,defined by the point A = 0, B

= 0, which

is a nuclear triple point. Figure 3 (right)takes these ideas and now casts themin the context of an extended symmetrytriangle [5]. Here U(5) corresponds tothe spherical solution, and the diagonalline from a point on the U(5)-SU(3) legto a point on the U(5)-SU(3) leg is thefirst order spherical-deformedtransition line. The line from O(6) downto this line is the prolate–oblatetransition line. Nuclei on opposite sidesof these two lines have differentequilibrium phases (symmetries).Where these two lines meet is theisolated triple point of second orderphase transition.

It is interesting to study how thesolutions given by the Hamiltonian ofEq. (2) behave across these first orderphase transitions. To do so we look atthe characteristic observable R

4/2 and

show, in Figure 4, predictions along theU(5) → SU(3) transition region and ofQ(2+

1 ) along the SU(3)-O(6)-SU(3)prolate–oblate transition region. In the

former, R4/2

increases from 2.0 to 3.33and the phase transition corresponds tothe point (η

value) of sharpest increase

(maximum of dR4/2

/dη). This featureimmediately discloses an importantaspect of structural evolution in thetriangle with the Hamiltonian of Eq. (2),namely, the highly nonlinear way inwhich structure changes en route fromthe U(5) vertex to the deformed SU(3)-O(6)-SU(3) leg. We will see this featurelater in our discussion of order andchaos. It implies, for example, that well-deformed nuclei (with, say, R

4/2~3.31)

actually appear quite far from the SU(3)vertex.

Along the SU(3)-O(6)-SU(3)transition region in Figure 4, Q(2+

1)changes from negative (prolate) topositive (oblate) at O(6). Here, thecritical point of the phase transition iscoincident with O(6) and marks thepoint where Q(2+

1) changes sign andQ(2+

1) /d|χ| peaks.For both transition regions, Figure

4 shows the behavior for two bosonnumbers 10 and 20, showing that thephase transition increases in sharpnesswith increasing N, as expected for aclassical phase transition [5]. Finally,Figure 4 includes examples of theempirical behavior for each of thesetransitions (Sm isotopes for U(5)-SU(3), and Hf-Hg isotopes for theprolate–oblate case). The behaviornicely mimics the calculations.(Detailed comparisons are shown in theoriginal literature [7].) Although datafor a prolate-oblate case are scarce anddo not reach fruition on the oblate sidebecause of the impending double shellclosure at 208Pb, there is a moderateincrease in Q(2+

1) going from Pt to Hg.Clearly, a fascinating quest in exoticnuclei would be to search for a fullprolate–oblate transition region. Withthe altered single particle levelsequences thought possible in weakly

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Figure 3. Landau analysis of nuclear phase transitions. On the left is a simplifiedrepresentation of the phases and first order phase transition lines correspondingto A = 0 and B

= 0 in Eq. (3). The axes are labeled by the traditional variables P,

T but would stand for the corresponding nuclear parameters in the presentdiscussion. The right side shows the application of this analysis to the equilibriumphases of nuclei, including the extension to oblate shapes. The symbol “t” denotesa nuclear triple point where two lines of first order phase transition meet.


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bound very neutron rich nuclei, thereare grounds for speculating that regionsof deformation might be more compactin N and Z and more prolate-oblatesymmetric.

There is much of interest in thetriangle and the Hamiltonian of Eq. (2)besides phase transitional behavior. Inparticular, the two parameters, η andχ, permit an explicit mapping of anynucleus onto the triangle (see Figure 2).η is a radius vector from U(5) towardthe SU(3)-O(6)-SU(3) side whereas χis an angle ranging from 0° (along theU(5)-SU(3) leg) to 30° (along the U(5)-

O(6) leg) to 60° (along the U(5)-SU(3)leg). By fitting the key observables inany given nucleus, it is thereforepossible to position it in the triangle.Such a mapping has recently been re-done, requiring that not only theproperties of the ground and γ bandsbe fit, as has normally been the case,but those of the 0+ band as well. In all,about 50 nuclei were included in thisnew mapping [8]. Their locations in thetriangle are shown in Figure 5 (left),where, for the purposes of laterdiscussion, we have re-oriented it to beconsistent with the literature and later

discussion (A few additional W and Osnuclei were also fit but are not includedin Figure 5).

This new mapping is quite different(primarily on account of the excellentfits to the 0+ states) than previous onesand it gives a new perspective onstructural evolution. There are three keyaspects of this. First, that evolution ismore complex, and Z-dependent, thanheretofore thought. Second, more rare-earth nuclei now occupy interiorpositions in the triangle. Third, the newmapping sheds insight into regularityand chaos in spectra of collectivenuclei. We now turn to this topic.

Chaos and Regularity

The existence of regular (integrable)and chaotic behavior in many-bodysystems forms a major theme in manybranches of physics. Atomic nucleiprovide an important testing ground forsuch behavior because of the variety ofstructures they exhibit and thedependence of these structures on thenumber of constituent nucleons.

Chaotic behavior in nuclei is usuallythought of in terms of high-temperaturesystems where shell structure melts.However, a decade ago [9] Alhassid andWhelan carried out an important studyof the chaotic behavior in nuclei at zerotemperature using the Hamiltonian ofEq. (2). As expected, they found thatthe level spectra are regular at and nearthe three dynamical symmetries U(5),SU(3), and O(6) of the model and thatchaotic behavior develops rapidly asone moves away from the symmetries.There were two exceptions to thisbehavior. The first, which is wellknown, happens between U(5) and O(6)and is connected to the conserved O(5)symmetry. The most fascinating result,however, was that there is anunexpected (“surprising” to use theirword) region of nearly regular behavior

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Figure 4. Behavior of observables across the two first order phase transitionsdiscussed in the text, the spherical–deformed phase transition and the prolate–oblate phase transition. Top: Calculated values of R

4/2 as a function of η for

χ =1

-7/2 for the spherical–deformed phase transition (left) and Q(2+1) as a function

of χ for η = 0 for the prolate–oblate phase transition (right). In the latter case

χ = 0 corresponds to the phase transition (analogous to B = 0 in the discussion ofLandau theory in the text) and to the dynamical symmetry O(6) as well. Thecalculations are performed for N = 10 (full line) and N = 20 (dashed line). Thelower part shows experimental data on R

4/2 for the Sm region and Q(2+

1) in theHf–Hg region and the line gives the theoretical values corresponding to the bosonnumber N, and the fitted η and χ values [7], together with a constant effectivecharge of 0.15 e.b.

72/


connecting SU(3) to U(5) along aninterior arc in the triangle which canbe approximately parameterized by therelation:

χ = 7 (η–1) – η

(7)

In the (η, χ) plane the location of theregular region is independent of theangular momentum for low to moderatevalues, and of the number of valencenucleons (i.e., the boson number N).Figure 5 (middle) shows the locationof the nearly regular region in theCasten triangle.

At that time of their work,unfortunately, there were no identifiednuclei corresponding to this newregular region and this finding thereforeremained merely a fascinatingtheoretical curiosity. However, therecent re-mapping of nuclei in the rareearth region radically changes thisconclusion. This is the third key aspectof the new mapping alluded to earlier.In fact, 12 rare earth nuclei were foundto fall very near the regular region [10].Figure 5 (middle) includes the locationin the symmetry triangle of these 12nuclei. Note that they span a widevariety of structures, indicated by thebounding R

4/2 values, ranging from an

anharmonic vibrator nucleus 156Er (R4/2

~ 2.3) to near perfect rotor nuclei (R4/2

~3.3), and to transitional nuclei in theW, Os region.

Regular and chaotic behavior weredistinguishable in the Alhassid–Whelananalysis by the distribution of nearestneighbor spacings of states in the samespin. Chaotic behavior is associatedwith the loss of good quantum numbers(except angular momentum) and henceof level mixing and avoided crossings.This leads to level repulsion and aWigner distribution of level spacings.In regular systems, one or more

quantum numbers remain valid (e.g.,the phonon-like quantum numbers ofO(5) along the U(5)-O(6) leg of thetriangle). Thus, there can be levelcrossings and Poisson distributions ofspacings result (high probability ofclose lying levels). This is illustratedin Figure 6, where the spectra of 0+

states are plotted for a typical value ofη

= 0.6, as a function of

χ for N

= 25.

For this situation, the regular region,where ~90% of all trajectories areregular, is centered at χ ~

–0.83. It is

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Figure 5. Left: Location of rare earth nuclei in the symmetry triangle. Note that to be consistent with the literature [9,10] thetriangle has been flipped and rotated so that U(5) is at the top. Middle: The arc of regularity in the triangle and the locationof the 12 nuclei identified as lying close to it. Right: Locus of near degeneracy of the 0+

2 and 2+

2 levels in the triangle.

Figure 6. Energies of 0+ states calculated with the Hamiltonian of Eq. (2) forη = 0.6 as a function of χ. The regular region, according to Eq. (7), is close toχ = –0.83 and is indicated by a dashed vertical line

[11].

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2 2

clear that, rather suddenly, the avoidedcrossings that appear for χ ≠ –0.8 valuesare replaced by nearly real crossingsnear χ ~ –0.8, as also occurs near χ ~ 0due to the O(5) symmetry.

The question arises what are theessential distinguishing features ofnuclei in or near the regular region? Themost characteristic and, indeed, unique,is the close spacing between the 2+

2 state

and the 0+2 state [10]. This applies

regardless of the structure. Note thatthis condition sometimes refers to statesof different intrinsic structure but inother cases to members of the samerotational band or phonon multiplet.

In the context of the commonly used2-parameter Hamiltonian of Eq. (2),which accounts quite well for structurethroughout the nuclear chart, the neardegeneracy of the 2+

2 and 0+

2 states is,

in fact, a unique indicator of the regularregion and is its most obviouscharacteristic. Indeed, as shown inFigure 5 (right), the locus of the regularregion in the triangle and the locus ofnear degeneracy of the 0+

2 and 2+

2 states

are almost identical. We note that theregular region does not correspond toan exact degeneracy but to close lying2+

2 and 0+

2 states and that, in the region

of the triangle where the 12 nuclei arelocated, this energy difference isslightly positive.

We also stress that, with Eq. (2), noother region of the triangle shows thisdegeneracy. Therefore, identification ofnearly degenerate 0+

2 and 2+

2 states can

be used to identify collective nucleinear the regular region. This kind ofdegeneracy of states belonging to twodifferent spin classes is, in fact, typicalof dynamical symmetries such as U(5)or SU(3) and therefore may provideclues as to the (currently unknown)nature of the underlying quantumnumber(s) and possible symmetry that

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may be approximately valid in theregular region.

Conclusion

In this review of new topics in theevolution of nuclear equilibriumshapes, we have traced a path linking anumber of seemingly diverse butintimately connected ideas. We studiedthe rich structures of a simpleHamiltonian of 2-parameter Ising type,including dynamical symmetries, phasetransitions, and regular and chaoticbehavior. We have explained usingLandau theory why the IBM exhibitsan isolated second-order phasetransition and continuous lines of first-order phase transitions. We stress that,although we have used the IBM, allthese results are quite general for anycollective model where the potentialcan be expanded in powers of β as inEq. (3). Moreover, it shows how thetheoretical framework of Landau theoryis quite universal, applicable to systemsas diverse as nematic liquid crystals andatomic nuclei.

This study relates to recentproposals of phase transitionalbehavior, critical points and criticalpoint symmetries along the U(5)-SU(3)and U(5)-O(6) legs of the triangle. Theexpanded triangle from the Landauanalysis allows the definition of anuclear triple point and symmetrizes thetriangle with respect to oblatedeformations. Its application to the Hf-Hg nuclei provides a new perspectiveon the evolution of nuclear structure inthis mass region. Applying thisHamiltonian to real nuclei we discusseda recent new mapping of structuralevolution in the rare earth region andexplained how this mapping reveals thesurprising existence of a set of nucleiwith regular behavior lying adjacent (inη, χ parameter space) to nuclei with

chaotic spectra. Finally, we discusseda unique empirical signature of thisregular behavior.

Acknowledgments

We acknowledge P. Cejnar,S. Heinze, A. Linnemann, E. A.McCutchan, P. Van Isacker, P. vonBrentano, V. Werner, and N. V. Zamfirwith whom parts of the work presentedhere were done. We also thank thecafeteria in the Köln Mensa wheremuch of this work was discussed anddeveloped. This work was supported bythe BMBF under Project number 06 K167, and US DOE Grant No. DE-FG02-91ER-40609.

References

1. E. Ising, Z. Phys., 31, 253 (1925).2. F. Iachello and A. Arima, The

Interacting Boson Model (CambridgeUniversity Press, Cambridge, England,1987).

3. F. Iachello, Nucl. Phys. NewsInternational, 2, No. 3,22 (1992).

4. L. Landau, Phys. Z. Sowjet., 11,26(1937); 11, 545 (1937); reprinted inCollected Papers of L. D. Landau(Pergamon, Oxford, 1965), p. 193.

5. J. Jolie et al., Phys. Rev. Lett., 89,182502 (2002); Phys. Rev. Lett., 87,162501 (2001), P. Cejnar et al., Phys.Rev., C68, 034326 (2003).

6. F. Iachello, Nucl. Phys. NewsInternational, 12, No. 3, 17 (2002).

7. J. Jolie, A. Linnemann, Phys. Rev. C,031301(R) (2003); O. Scholten, F.Iachello, and A. Arima, Ann. Phys.(N.Y.), 115, 325 (1978).

8. E. A. McCutchan, N. V. Zamfir andR. F. Casten, Phys. Rev., C69, 064306(2004); E. A. McCutchan, N. V. Zamfir,submitted to Phys. Rev. C.

9. Y. Alhassid and N. Whelan, Phys. Rev.Lett., 67, 816 (1991).

10. J. Jolie et al., Phys. Rev. Lett., 93,132501 (2004).

11. S. Heinze et al., to be publ.

Application of Low Energy Spin Polarized Radioactive

Ion Beams in Condensed Matter Research

facilities and methods

Introduction

The new ISAC facility at TRIUMF(Canada), produces some of the world’smost intense radioactive ion beams(RIBs). Although the primary scientificmotivation for these facilities lies innuclear physics and nuclearastrophysics, RIBs also haveapplications in condensed matter (CM).Many pioneering CM experiments havealready been performed at the ISOLDEfacility (CERN). Continuing on thispath at ISAC we have recentlypolarized a beam of 8Li+ to be used asa magnetic probe of ultra-thin films andinterfaces. We report here on progressin developing this new application oflow energy RIBs, which is based on thetechnique of β-detected nuclearmagnetic resonance (β-NMR).

Conventional NMR is a powerfultechnique for probing the local electric/magnetic properties of materials [1]However, NMR typically requires alarge number (1018) of nuclear spins togenerate a signal. Consequently it ismost widely used in studies of bulkmaterials. A much greater sensitivitycan be obtained with β-NMR where thesignal is detected through the β-decayof a polarized radioactive nucleus. Forexample, in the case of 8Li, which hasa mean lifetime of 1.2 s, an energeticelectron is emitted preferentially in thedirection opposite to the nuclearpolarization. Such β-decay anisotropywas first used to demonstrate parityviolation in weak interactions in 1957[2]. Since then β-NMR has been usedextensively to measure nuclearmoments of unstable isotopes. Incondensed matter β-NMR allows oneto simulate the behavior of stable

isotopes with unprecedented sensitivity[4,5] For example, in semiconductorsa radioactive nucleus is ideally suitedto characterizing the behavior of anisolated impurity where conventionalNMR lacks the required sensitivity [6].Intense low energy beams of highlypolarized ions, now available at ISAC,present new opportunities in condensedmatter research. In particular, becauseonly about 107 spins are needed togenerate a β-NMR signal, the methodis well suited for studies of nano-structures and ultra-thin films wherethere are few host nuclear spins.Furthermore, with the unique polarizedion beam now at ISAC, it is possible tovary the mean depth of implantation ona lengthscale of nanometers. The

scientific applications are similar towhat is now possible with low energymuon beams [8]. However, the positivemuon and a radioactive nucleus are verydifferent probes and thus providecomplementary information [9]. Inaddition RIBs from an ISOL target arenaturally created at low energy and canbe orders of magnitude more intensethan a low energy muon beam.

β-NMR has close similarities toboth muon spin rotation andconventional NMR. The two basicobservables are the spin precessionfrequency and spin relaxation rate, bothof which are used to monitor the localelectronic/magnetic environment. Aschematic of a typical β-NMR setup isshown in Figure 1a. Similar to muon


Figure 1. (a) A schematic of a β-NMR experiment. The initial polarization caneither be perpendicular to the beam direction or parallel as shown here. Plasticscintillation detectors (F and B) are used to monitor the β-decay asymmetry as afunction either of (b) RF frequency with a continuous beam or (c) time with apulsed beam. The two different curves in (b) and (c) correspond to two differentbeam helicities.


spin rotation, the experiment is carriedout by implanting spin polarizedparticles (ions) into the sample. A staticexternal magnetic field (H

0) is applied

along the initial spin polarizationdirection z while an oscillatingtransverse magnetic field (H

1 cos 2Zνt)

is stepped through a range offrequencies around the Larmorfrequency of the nucleus (ν

L=γB),

where B is the local magnetic field atthe nuclear site and γ is thegyromagnetic ratio. The time averagednuclear polarization P

z, is directly

proportional to the β-decay asymmetry:

(1)

where F(ν) and B(ν) are the number ofcounts in the F and B detectors atfrequency ν (corrected for the slightlydifferent efficiencies of the detectors).The proportionality constant A ≈ 0.15depends on the beam polarization, β-decay characteristics, and variousinstrumental parameters. Theresonances are detected by measuringthe β-decay asymmetry as a functionof ν. A decrease in P

z occurs when ν is

matched to the nuclear spin splittingsubject to the usual magnetic dipoleselection rule δm = ± 1 (see Figure 1b).The position of the β-NMR resonanceis a precise measure of the localmagnetic field at the site of the nucleuswhich depends on the local electronicstructure and static spin susceptibilityof those electrons. Alternatively one canmeasure the 1/T

1 nuclear spin relaxation

rate by implanting a short beam pulseand measuring the time evolution of thepolarization (see Figure 1c). The spinrelaxation rate is sensitive to theelectron spin dynamics. Of course ingeneral the presence of the impuritywill alter the local electronic structure.

However, studies with muons haveshown that the temperature dependenceand magnetic field dependence of thefrequency shifts and spin relaxationrates are often the same as thosedetected using the host nuclear spins.

Recently we have also performedthe first zero field β-NQR (NuclearQuadrupole Resonance) experiment,which is done in the absence of a staticmagnetic field (H

0=0). It is well known

that if a nucleus with an electricquadrupole moment, such as 8Li , restsin a crystalline site with non-cubicsymmetry, there will be a quadrupolarsplitting of the nuclear spin levels evenin zero external magnetic field. One caninduce transitions between these levelswith the oscillating magnetic field (H

1),

and thereby alter the nuclear spinpopulation. The ability to performmagnetic resonance in zero appliedfield has important applications forstudies on exotic magnetism andsuperconductivity. It is also remarkablethat the 8Li NQR resonances are narrow(few kHz) and easily observed atacoustic frequencies. Recall that inconventional NQR the signal to noiseratio degrades rapidly with decreasingfrequency, and has a practical lowerlimit of a few MHz.

The β-NMR and β-NQR resultsfrom ISAC demonstrate that a lowenergy polarized beam of 8Li can beused as a sensitive probe of themagnetic properties of thin films andinterfaces where it is very difficult toobtain equivalent information withconventional NMR. Although the rangestraggling for such ions is large (of theorder of the range) the average depthcan be controlled very precisely in the5–200 nm range.

β-NMR Probes at ISAC

At the TRIUMF ISAC facility theprimary 500 MeV proton beam is used

to produce the radioactive ions. A widevariety of isotopes are released from thesurface ionization source heated to2000oC but alkalis are preferentiallyionized because of their low ionizationenergy. The resulting positive ions arethen accelerated to 30 keV forming alow emittance beam with an energyspread of 1–2 eV. The beam is thenpassed through a high resolution massspectrometer so that only the isotopeof interest reaches the experimentalarea.

Although any β-emitting nucleuswith non-zero spin can be studied withβ-NMR, the number of isotopessuitable as a probe in condensed matteris much smaller. The most essentialrequirements are: (1) a high productionefficiency, (2) a method to efficientlypolarize the nuclear spins, and (3) ahigh β-decay asymmetry. Otherdesirable features are: (4) low massto reduce radiation damage onimplantation, (5) a small value of spinso that the βNMR spectra are relativelysimple, and (6) a radioactive lifetimethat is not much longer than a fewseconds. Table 1 gives a short list ofthe isotopes we have identified assuitable for development at ISACwhere production rates of 106/s areeasily attainable. Our initial efforts havefocused on 8Li (I = 2), which is thelightest suitable isotope for β-NMR.The low mass means that the implanted8Li rests at crystalline sites away fromany radiation damage. Also the meanlifetime (1.2s) is comparable to typicalnuclear spin relaxation times in manymaterials. In addition, both thegyromagnetic ratio (γ = 6.3 MHz/T) andelectric quadrupole moment of 8Li (Q= +33 mB) are small so that hyperfineinteractions with the crystalenvironment are weak. For example, inmetals we expect small metallicfrequency shifts in the 100 ppm range;


whereas, the electric quadrupolarsplittings at non-cubic sites should beonly 10s of kHz. Thus, with narrowresonances and relaxation rates slowcompared to heavier nuclei, we expectthat 8Li will act as a high resolutionprobe of internal magnetic fields insolids. Although the intrinsic resolutiondetermined by the 8Li lifetime and itsgyromagnetic ratio is a few mG, the linebroadening in solids limits this to about500 mG. Nevertheless, this is an orderof magnitude greater than is possiblewith muon spin rotation.

Polarized 8Li Beam

Large nuclear polarization of thelow energy 8Li+ beam is created using

a fast collinear optical pumpingmethod, which is well-established forthe case of alkalis. A schematic of thepolarizer at ISAC is shown in Figure 2.Continuous circularly polarized lightfrom a single frequency ring dye laser(300mW power) is directed along thebeam axis [10]. The first step in theprocedure is to neutralize the ion beamby passing it through a Na vapor cell.The neutral beam then drifts 1.9 m inthe optical pumping region in thepresence of a small (1 mT) longitudinalmagnetic field. The D

1 atomic transition

2s2S1/2

→ 2p2P1/2

of neutral Li occurs at671 nm. After about 10–20 cycles ofabsorption and spontaneous emission,a high degree of electronic and nuclear

spin polarization is achieved. The finalstep is to strip off the valence electronby passing it through a He gas cell [11].The polarized 8Li+ beam can then beguided electrostatically to one of thespectrometers without affecting thenuclear spin polarization. Typically thepolarization of the beam is about 70%and very stable on the time scale of ameasurement. The spectrometers arepositioned so that the polarizationdirection is parallel to the high fieldspectrometer and transverse to the axisof the beam entering the β-NQRspectrometer.

The final electrostatic elements ofthe beamline are used to focus and steerthe beam to the sample. This tuning isachieved by placing a plastic scintillatorat the sample position and viewing itwith a CCD camera. 8Li decays to 8Be,which in turn promptly decays into twoenergetic alphas of 1–2 MeV. Theresulting light emitted from thescintillator is easy to detect withexposure times of about 1 s. Analysisof the images (see Figure 3) indicatesthat more than 95% of the beam fallswithin 4 mm diameter. This defines the



Table 1. Examples of isotopes suitable for β-NMR. The production rates areprojections except in the case of 8Li.

Isotope Spin T1/2

γ Maximum β-Decay Production

(s) (MHz/T) Asymmetry rate (s–1)

8Li 2 0.8 6.26 0.33 108

11Be 1/2 13.8 22 0.33 107

15O 1/2 122 10.8 0.7 108

17Ne 1/2 0.1 0.33 106

Figure 2. A schematic of the ISAC polarizer. A 30 keV 8Li+ ion beam is neutralizedin the Na cell and then reionized in the He cell. In the intermediate drift region, adye laser is used to pump the D1 optical transition of the 8Li atom with circularlypolarized light. The resulting polarized ion beam is guided to either the β-NQRspectrometer or the high field β-NMR spectrometer

Figure 3. 8Li beamspot image from asmall scintillator in the high fieldspectrometer observed with a CCDcamera. More than 95% of the beam isestimated to fall within a 4 mm diameter.

minimum area of a sample that can bestudied.

The nominal energy of the beam (30keV) corresponds to an averageimplantation depth of about 200 nm.However, the β-NMR spectrometer sitson a high voltage platform so that theenergy of implantation can be adjusted.Recently we have demonstrated that itis possible to decelerate such a beamdown to 84 eV. A similar platform iscurrently being designed for the β-NQRspectrometer. In this way it is possibleto measure resonances as a function ofimplantation depth in the range of 5–200 nm.

Spectrometers

High Field β-NMR SpectrometerA schematic of the spectrometer is

shown in Figure 4. The polarized beamenters from the left and passes througha hole in the back detector beforeentering the last Einzel lens at theentrance to the high-homogeneity 9 Tsuperconducting solenoid. The beamspot at the center of the magnet is asensitive function of the Einzel lens

voltage, magnetic field, and beamenergy.

The spectrometer has longitudinalgeometry, such that the polarization andmagnetic field are both along thebeam axis. This is necessary for

measurements in high magnetic fields,where both the incoming ions andoutgoing betas are strongly focused bythe magnet. The forward detector is onthe beam/magnet axis and is locatedseveral cm downstream of the sample.In order to detect betas in the backwarddirection (opposite to the beamdirection), it is necessary that thedetector be outside the magnet becausethe betas are confined to the magnetaxis while inside the magnet bore.Although the solid angles subtended bythe two detectors in the zero field arevery different, they have similardetection efficiencies in high magneticfields due to this focusing effect.

The spectrometer and final leg of thebeamline are UHV (ultra high vacuum)compatible in order to avoid a buildupof residual gases on the surface of thesample. Differential pumping is used toreduce the pressure from 10-7 torrupstream of the spectrometer to 10-10 torrin the main chamber. The sample



Figure 4. A schematic of the high field β-NMR spectrometer. The beam passesthrough a small hole in the B detector and then is focussed onto the sample in thebore of a 9T superconducting solenoid.

Figure 5. Photograph of the spectrometer on the high voltage platform. The bellowshas been extended so that the sample and cryostat is in the loading position.

cryostat is mounted on a large bellows,so that it can be withdrawn from themagnet bore in order to change thesample through a load lock on top of themain vacuum chamber. The photographin Figure 5 shows the magnet, bellows,and load lock from the back end. Figure6 shows a gold foil being loaded intothe UHV chamber through the lock.Plastic scintillation detectors are usedto detect the betas from 8Li → 8Be + ν

e

+ e–, for which the end point energy is13 MeV.

β-NQR spectrometerThe β-NQR spectrometer is less

complicated. The beam enters the ultrahigh vacuum chamber with initialpolarization transverse to the beamdirection. The β’s pass through thinstainless steel windows and are detectedin left and right detectors placedsymmetrically on either side of thesample and parallel to the initialpolarization direction. A set of threemagnetic coils are present that allowone to apply a static uniform magneticfield (0–15 mT) along the initialpolarization direction, or to zero the

field to within 0.005 mT. The oscillatingH

1 field is applied in the vertical

direction which is perpendicular to both



the beam and polarization direction.

Example Results

β-NMR in a Ag Film on a MgO SubstrateDepth profiling with β-NMR was

demonstrated by implanting the beaminto a 19 nm–thick Ag film grown on asingle crystal of MgO. The sample wasprovided by T. Hibma from theUniversity of Groningen. Figures 7band 7c shows the resulting β-NMRspectra for two different implantationenergies. In Figure 7c the high voltageplatform is grounded so that the 8Listops almost entirely in the MgOsubstrate. At all temperatures a singlenarrow line is observed in the MgO.The absence of any quadrupolarsplitting indicates that the electric fieldgradient at the stopping site is almostzero as expected for the tetrahedral

Figure 6. Photograph of the gold foil being loaded into the UHV vacuum chamberof the high field β-NMR spectrometer.

Figure 7. β-NMR spectra on a 20 nm of epitaxially grown Ag film on a MgOsubstrate. In (c) the implantation energy is 30 keV so that the signal comes fromthe MgO substrate. The resonance position in MgO is determined primarily bythe applied magnetic field because it is an insulator and the chemical shifts areonly a few ppm. In (b) the energy of implantation is 1 keV so that a significantfraction of the beam stops in the Ag film. The two additional resonances areattributed to Ag where hyperfine coupling to the conduction electrons produces asite-dependent Knight shift. The higher frequency line is attributed to theoctahedral interstitial site whereas, the lower frequency line is due to 8Li at asubsitutional site.

(a)

(b)

(c)



interstitial and substitutional sites. Theposition of the resonance is determinedby the applied field because the localstatic susceptibility in a non-magneticinsulator is small. The frequencyspectrum in Figure 7b is taken with theplatform voltage set to 1 keV below thebeam energy. In this case most of thebeam stops in the Ag film. The residualMgO signal is attributed to part of thebeam that lands in an area of the thesubstrate not covered by the film. Twoadditional resonances in Figure 7boccur at slightly higher frequencies andare attributed to 8Li in the thin Ag film.Again the absence of quadrupolarsplittings imply that both resonancesoriginate from sites with cubicsymmetry. The resonances are shiftedrelative to MgO due to the hyperfineinteraction with the conductionelectrons of Ag. These metallic“Knight” shifts are on the order of a fewhundred ppm as expected for a light ionsuch as Li. A recent study of these linesas a function of temperature concludesthat the higher frequency line comesfrom 8Li at the octahedral interstitial site(labeled O in Figure 7a), whereas thelower frequency resonance is from thesubstitutional site [22] (labeled S inFigure 7a). The lines are remarkablysharp, confirming that the implanted Liresides in sites that are well away fromany radiation damage.

There are several applications ofthis result. Because Ag is relatively inertand can be easily evaporated onto anysurface, one could use the β-NMRresonance to measure the magnetic fielddistribution near the surface of amaterial with a resolution of about 0.5G. In this way the polarized low energybeam can be used as a kind of localmagnetometer. For example, one coulduse this method to characterize thevortex lattice near the surface of asuperconductor. Also, conventional

NMR of small metallic particles hasrevealed interesting but poorlyunderstood confinement effects [18]Such finite size effects may beelucidated by doing β-NMR on thinmetal films, wires, or dots.

β-NQR in SrTiO3

In many materials the local sitesymmetry in less than cubic. In this casethere is an electric field gradient at the8Li nucleus that couples to the smallelectric quadrupole moment of 8Li andproduces an energy splitting betweenthe nuclear spin states in the zeromagnetic field. This complicates the β-NMR spectrum in an applied field andcan lead to many small resonances.However the simplicity is restored inzero applied field where the spinHamiltonian reduces to:

Hq = Hν

q[I2

z – 2] (2)

Here νq= e2qQ/8, eq = ν

zz is the electric

field gradient (EFG), Q is the electricquadrupole moment of the nucleus, andz is symmetry axis of the EFG tensor.

The energy eigenvalues Em

= hνq

(m2 – 2) are a function of the azimuthalquantum number m where I

z|m>=

m|m>. In the zero applied field there aretwo resonant frequencies (for I = 2) atν

q and 3ν

q corresponding to the allowed

magnetic dipole transitions0 ↔ ±1 and ±1 ↔ ±2, respectively. Theamplitude of each resonance is directlyproportional to the induced change inthe nuclear spin polarization P

z(ν) on

resonance.Figure 8 shows the β-NQR

spectrum taken on a single crystal ofSrTiO

3, which is a common substrate

used in the growth of thin films such ashigh Tc superconductors. A largeresonance occurs at a frequencycorresponding to 3ν

q. Note that 80% of

the polarization is destroyed onresonance. This is about 10 times largerthan the amplitude estimated assumingthe simple spin Hamiltonian above.This amplification of the resonance canbe explained with a slightly non-axialelectric field gradient at the Li site,which leads to mixing of the m = ±1states and causes most of polarization

Figure 8. The β-NQR spectrum obtained for a SrTiO3 single crystal at room

temperature in zero external field. The resonance occurs when the frequency ofH

1 equals 3v

q corresponding to the m=2 to m=1 quadrupolar transition frequency.

The inset shows the location of the Li ion at the face center of the cube.

to be destroyed on resonance [23]β-NQR also has many applications

because it can be done in a zero staticapplied field. For example one can useit to characterize the superconductivitynear the surface or interface of a highTc superconductor. Under certaincircumstances we expect thesuperconductivity to be different nearthe surface than in the bulk. Sometheories predict a broken time reversalsymmetry leading to small magneticfields that would be evident in the β-NQR spectrum

Summary and Conclusion

We have demonstrated that it ispossible to carry out β-detected NMRand β-detected NQR using a beam oflow energy, highly polarized 8Li+.Depth profiling of the signals can bedone on a nanometer scale. Weanticipate that the technique will havemany applications in studies of ultra-thin films, interfaces, and other issuesrelated to electron confinement whereit is difficult to obtain equivalentinformation using conventional NMR.

Acknowledgments

This work was supported by theCIAR, NSERC, and TRIUMF. We alsowish to acknowledge many people atTRIUMF who have helped make theseexperiments possible, especiallyDonald Arseneau, Rick Baartman,Suzannah Daviel, Syd Kreitzman, andRene Poutissou. We also thank RahimAbasalti and Bassam Hitti for superbtechnical support. Finally, we thankLaura Greene for providing the SrTiO

3

sample and T. Hibma for the Ag film.

References

1. C. P. Slichter, in Principles of MagneticResonance, third ed., Springer-Verlag,New York, 1990., pp. 485–500.

2. C. S. Wu et al., Phys. Rev., 105, (1957)1413.

3. R. F. Kiefl et al., Physica B 289–290(2000) 640–647.

4. H. Ackermann, P. Heitjans and H.-J.Stöckmann in Hyperfine Interactions ofRadioactive Nuclei J. Christiansen, ed.,Topics in Current Physics Vol. 31(Springer, Berlin, 1983), p. 291.

5. P. Heitjans, W. Faber, A. Schirmer,J. Non-Cryst. Solids 131 (1991) 1053–1062.

6. B. Ittermann, G. Welker, F. Kroll, F.Mai, K. Marbach, and D. Peters, Phys.Rev. B 59 (1999) 2700.

7. T. R. Beals et al., Physica B 326 (2003)205.

8. E. Morezoni, et al Physica B 326 (2003)196.

9. R.F. Kiefl et al., Physica B 326 (2003)189–195.

10. M. Keim, U. Georg, A. Klein, R.Neugart, M. Neuroth, S. Wilbert, P.Lievens, L. Vermeeren, and theISOLDE Collaboration, HyperfineInteractions 97–98 (1996) 543.

11. C. D. P. Levy et al., NIM B 204 (2003)689–693.

12. M. H. Cohen and F. Reif, QuadrupoleEffects in Nuclear Magnetic ResonanceStudies of Solids, Solid State Physics5, (1957) 321–438.

13. T. P. Das and E. L. Hahn, NuclearQuadrupole Resonance Spectroscopy,Academic Press Inc. (1958).

14. C. H. Townes and A. L. Schawlow,Microwave Spectroscopy, McGraw-HillBook Company (1955).

15. W. A MacFarlane et al., Physica B 326(2003) 209.

16. W. Körner et al., Phys. Rev. Lett., 49(1982) 1735.

17. Y. Inaguma et al., J. Electrochem. Soc.,142 (1995) L8; and Solid State Ionics79 (1995), 91.

18. H. Brom and J. J. van der Klink, Prog.NMR Spect. 36, 89 (2000) andreferences therein.

19. Ch. Niedermayer et al., Phys. Rev. Lett.,83 (1999) 3932 .

20. H. Hoffsass and G. Lindner, Phys. Rep.,201 (1991) 121.

21. M. Füllgrabe et al., Phys. Rev., B 64224302 (2001) and references therein.

22. G. D. Morris, W. A. MacFarlane, K. H.Chow, R. F. Kiefl, Z. Salman, D. J.Arseneau, A. Hatakeyama, S. R.

Kreitzman, C. D. P. Levy, R. Poutissou,R.H. Heffner, J.E. Elenewski, L. H.Greene, Phys. Rev. Lett., 93 (2004)157601.

23. Z. Salman, E. P. Reynard, W. A.MacFarlane, J. Chakhalian, K. H. Chow,S. Kreitzman, S. Daviel. C. D. P. Levy,R. Poutissou, and R. F. Kiefl, Phys. Rev.,B 70 (2003) 104404.

R.F. KIEFL

TRIUMF, Vancouver, BC, Canadaand Department of Physics

and AstronomyUniversity of British Columbia,

Vancouver, BC, Canadaand Canadian Institute for

Advanced Research,Canada

K. H. CHOW

Department of PhysicsUniversity of Alberta

Edmonton, AB, Canada

W. A. MACFARLANE

Department of Chemistry,University of British Columbia,

Vancouver, BC, Canada

G. D. MORRIS

C. D. P. LEVY

Z. SALMAN

TRIUMF Vancouver, BC, Canada



meeting reports

Report on the 8th Nuclei in the Cosmos Conference

The 8th Nuclei in the Cosmosconference was held from July 19 toJuly 23, 2004 at the Coast Plaza Hotel,located in the English Bay area ofVancouver, British Columbia, Canada.Hosted by TRIUMF (Canada’sNational Laboratory for Nuclear andParticle Physics) and chaired by L.Buchmann, approximately 273registered participants (~30% female)were treated to the latest news from theworld of nuclear astrophysics andrelated fields. This series of conferenceswas established in 1990 with theinaugural meeting being held in Austria.The early emphasis on experimentalnuclear astrophysics has now beenextended to include a wide range oftopics from observational astronomy tostellar modeling under extremeconditions.

The conference was started in aunique fashion with Tom Lehrer’srendition of “The Elements”; as thefocus of these meetings is the origin ofthe elements in the universe. Openingtalks on core collapse supernovae (SN)of massive stars reported significantadvances in understanding thesemechanisms that have led to a workingmodel of such SN explosions althoughcalculations with the most advancedphysics have difficulties simulating anexplosion. Additional data on electroncapture rates for the iron group nucleiare needed. The observation of thegamma emitting isotope, 26Al (t

1/2 = 7.4

× 105 yr) resulting from SN (and otherexplosive events) has stimulated thedrive to measure reaction rates for itsproduction and destruction in suchevents. However, it is not understoodwhy 60Fe has not yet been observed byγ-ray astronomy.

An exciting development was the

Participants at the Nuclei in the Cosmos 2004 Conference

observation of the 60Fe (t1/2

= 1.5 Myr)in ferromanganese crust in the Pacific.This isotope can only have beenproduced in a SN explosion thatoccurred in the solar vicinity at in thepast 3 Myr. The Cosmic Ray IsotopeSpectrometer (CRIS) on ACEspacecraft, measuring the isotopiccomposition of cosmic rays, observesa source similar to the elements in thesolar system. Since 2002 the EuropeanSpace Agency’s INTEGRAL satellitehas been observing gamma rays emittedfrom specific isotopes in our Galaxy,including annihilation radiation and26Al. Such astronomical observationsare putting hard constraints onmechanisms and pushing for moreprecise experimental measurements inthe laboratory.

The reaction considered the mostimportant in the understanding of theproduction of elements in stellarenvironments is 12C(α,γ)16O. It is thesubject of many experimental studiesthat attempt to measure its rate at stellartemperatures with greater precision.Although significant progress has been

achieved by various groups, more workis needed.

The LUNA (Laboratory Under-ground for Nuclear Astrophysics)facility, located in the Gran Sasso tunnelin Italy, allows measurements ofimportant reactions such as radiativeproton capture on 14N at very lowenergies. With the reduction of cosmicray background, studies down to theGamow energy window can beachieved.

A highlight of the conference wasthe series of talks on SN and gamma-ray bursts (GRBs), exhibiting energiesof ~1052 ergs. Overwhelming evidenceover the last 6 years indicates that alarge fraction of GRBs areaccompanied by SN Ic, although theinverse is not necessarily true. Modelsof such violent explosions (collapsemagnetar) were presented as a work inprogress; the role of rotation and theemission of jets are important aspectsof such scenarios. Of equal importanceis a good understanding of SN 1a,which are excellent cosmologicaldistance indicators (standard candles)



meeting reports

but more effort is needed on theirexplosion physics.

Considerable progress has beenmade in understanding the s-process butmore work is needed especially withinitiation reactions and for reactions oflow cross-section and at very lowenergies. A new facility, the n_TOFsystem at CERN, is now operationaland providing valuable (n,γ) cross-sections over a wide mass range andenergies.

A number of talks were centered onthe r-process in SN explosions, whichis believed to be the mechanismresponsible for the production of halfof the elements heavier than iron.Identification of the astrophysical siteand the specific conditions under whichthe r-process takes place remains amajor mystery, along with predictionsof properties of very neutron-rich exoticnuclei involved in this process.

There were a number of overviewtalks on experimental studies with both

stable and radioactive heavy ion beams.Areas of focus are measurements forthe r-process, the rp-process and the p-process. The combination of these datacoupled with improved stellar modelslead to a better understanding ofnucleosynthesis in stellar environmentsprior to and during explosive scenarios.Studies on presolar grains are alsoproviding a wealth of new informationand setting constraints on models ofnucleosynthesis and stellar evolution.

Mechanism of cataclysmic stellarevents, including novae and X-raybursts, were the subjects of various talksat the conference. New techniques inthis area involve radioactive beams andrecoil separators (such as DRAGON atTRIUMF) are providing new avenuesto obtain necessary informationpreviously considered inaccessible.Additional reaction rates involvingexotic nuclei are still required for aclearer understanding of the mechanismleading to the production of particular

elements.In addition there were talks on

reactions occurring in the sun,measurements of the solar neutrino fluxusing the Sudbury NeutrinoObservatory (SNO), and the status ofinformation of reactions in Big Bangnucleosynthesis.

At the banquet held at the Universityof British Columbia’s Museum ofAnthropology, all were treated to anintrospective view of the early days ofstudies at the first center ofexperimental nuclear astrophysics atCaltech by D. D. Clayton. His talk wasentitled, “Phive Years of Physics Phunwith Phowler,” presenting stories ofworking with Willie Fowler (NobelLaureate in 1983).

The next conference will be hostedby CERN in 2006.

JOHN M. D’AURIA

TRIUMF, Canada

International Conference on Nuclear Data for Science

and Technology

The scope of the extensive field ofnuclear data is remarkably little knownin the nuclear physics communityexcept for a few products includingcharts of the nuclides, tables ofisotopes, nuclear wallet cards, nuclearstructure files, and nuclear structurereferences. How these products arecreated is even less well known. Forapplications extending from the designof basic physics experiments toresearch and development of nucleartechniques and effects in energy, space,medicine, geology, homeland security,and so forth, detailed information on thestructure and interactions of nuclei isessential. Fortunately for nuclear

scientists and engineers, there is anextensive international effort onimproving the knowledge of thesefundamental data and on making thesedata accessible to all.

In the artistic and historic city ofSanta Fe, the International Conferenceon Nuclear Data for Science andTechnology (“ND2004”) was held onSeptember 26–October 1 2004. ThisConference focused on nuclear data,their production, compilation,evaluation, dissemination, testing, andapplication. The data are produced boththrough experiment and theoreticalmodels; they are compiled andevaluated to form data libraries for use

in applications; they are tested throughbenchmark experiments; and they areused in a very wide range ofapplications. This Conference includedall of these activities with the goal ofimproving nuclear data, identifyingareas of data needs where progress isrequired, and providing reliable data forapplications including fission andfusion energy, accelerator-drivensystems, accelerator technology,spallation neutron sources, nuclearmedicine, environment, geologicalexploration, space, nonproliferation,nuclear safety, astrophysics andcosmology, and basic research.

This conference was part of a series,

held in recent years under the auspicesof the OECD Nuclear Energy Agency,with preceding meetings in Harwell(1978), Gaithersburg (1979), Antwerp(1982), Santa Fe (1985), Mito (1988),Juelich (1991), Gatlinburg (1994),Trieste (1997), and Tsukuba (2001).The present meeting was attended by445 participants from 31 countriesincluding the USA (187), Japan (52),Russia (34), France (28), Germany(25), and Belgium (14). The meetingreceived support from the Los AlamosNational Laboratory; the U.S.Department of Energy’s NationalNuclear Security Adminstration, Officeof Science, and Office of NuclearEnergy, Science and Technology; theInternational Atomic Energy Agencyand exhibitors. The program consistedof 1 banquet speech, 4 plenary talks,71 invited talks, 84 contributed oraltalks, 1 invited panel, and 326 posters.

Highlights of the meeting includednew experimental facilities andtechniques, significant improvementsin nuclear reaction models, deve-lopments in fundamental physics,continuing improvements and tests ofnuclear data libraries, enhanceddissemination of nuclear data, increasedemphasis on integral experiments asconstraints on the microscopic data,

meeting reports

much wider use of computersimulations, and increased confidencein these simulations from well-characterized benchmark experiments.An indication of the scope of theconference is given by the four plenarytalks: Phillip Finck (Argonne)“Developments in Nuclear EnergyTechnologies and Nuclear DataNeeds”; Dirk Dubbers (Heidelberg andGrenoble) “Particle Physics with ColdNeutrons”; Rick Norman (Berkeley andLivermore) “An Eclectic Journeythrough Experimental Physics, or HowI Learned to Stop Worrying and LoveNuclear Data”; and James Ziegler (U.S.Naval Academy) “The Importance ofNuclear Data to Modern Technology.”Prof. D. Allan Bromley gave thebanquet speech on “Advising thePresident.” Memorial sessions wereheld as tributes to the extensivecontributions of S. Raman (Oak Ridge)and S. Pearlstein (Brookhaven) to thisfield.

Nuclear data are available to usersaround the world through a number ofnuclear databases that contain the mostprecise information available on nuclearstructure properties and nuclear reactioncross-sections. The ENSDF (EvaluatedNuclear Structure Data File) ismaintained and improved via an

international collaboration, and manypapers were presented describingvarious advances in this database.Nuclear cross-sections are provided ina number of databases in differentregions of the world. The U.S. cross-section data are given in the ENDF file,and those from Europe, Russia, Japan,and China are the JEFF, BROND,JENDL, and CENDL files, respectively.Many talks addressed cross-sectionimprovements in these files. A newrelease of ENDF, the ENDF/B-VII, isscheduled for 2005, and much attentionwas paid to presenting advances in thisdatabase and the integral data testingused to validate these data. These cross-section databases are used by radiationtransport codes for design andsimulation in nearly all nucleartechnologies.

The program and abstracts ofND2004 can be found at the Con-ference website: http://t16web.lanl.gov/nd2004/. Proceedings will be publishedby the American Institute of Physics.The next conference in this series,ND2007, is anticipated to be held inFrance in May 2007.

ROBERT C. HAIGHT

AND MARK B. CHADWICK

Co-chairs, ND2004,Los Alamos National Laboratory


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NSAC Activities—2003/2004

The Nuclear Science AdvisoryCommittee (NSAC) plays a role in theU.S. somewhat analogous to that ofNuPECC in Europe although these twocommittees function differently. NSACdirectly advises the two nuclear physicsfunding Agencies, the U.S. Departmentof Energy (DOE) and the NationalScience Foundation (NSF). NSAC istypically comprised of about 17members, representing universities andnational labs, experimentalists andtheorists, and reflecting the diversity inthe field. NSAC receives tasks orquestions (“charges”) from theseAgencies to study various specifiedissues and to give guidance. Often,these charges are requests to look intocertain sub-fields, to identify the mostpromising scientific opportunities, thefacility and detector requirements torealize them, and to make recom-mendations to optimize current andfuture investments in the field.Frequently, these charges are framed inthe context of particular fundingscenarios.

Given a charge, NSAC forms a sub-committee that studies the issue at hand,and writes a Report that is submitted toNSAC. NSAC meets to evaluate theReport and, usually, to transmit it to theAgencies with its concurrence and withan accompanying letter expressingNSAC’s perspective as well. Oncetransmitted, these Reports are publiclyavailable on the Agencies’ websites.Every six years or so, NSAC alsoorganizes a decadal Long RangePlanning process for the field as awhole.

The advice given by NSAC throughthe work of its sub-committeescontributes valuable guidance and isoften reflected in subsequent fundingdecisions, new initiatives, and alteredpriorities. Although the output ofNSAC’s work is advisory only, andfunding constraints may limit therealization of its recommendations, theAgencies seldom act contrary to thoserecommendations and thus NSACplays a significant role in developingU.S. funding priorities for nuclearscience.

The years 2003/2004 have beenamong the most active ever for NSAC.There have been a total of 8 charges, aslisted in Table 1 by short titles and thesub-committee chairs. The first on thelist, the Facilities Report, played asignificant role in the development ofthe well known 20 Year Facilities Planfor the DOE, with its very high rankingfor RIA. Other charges dealt withfundamental physics with neutrons,nuclear theory, the relation of RIA andGSI in the exotic beam field, andopportunities for new advances inrelativistic heavy ions. A few charges

differed in character from these. Oneof these dealt with the development ofa set of Milestones and phasedPerformance Measures for each sub-field over the next decade, for use bythe funding Agencies in theirassessment of progress in the field.Another, the so-called Committee ofVisitors, turned the peer review tableson DOE to some extent, providing anevaluation of the operations andprocesses of the Nuclear Physics Officeof the Office of Science at the DOE.Finally, a third change dealt broadlywith education and public outreach innuclear science, with recommendationsspanning the gamut from the earliestschool years through the post-docperiod, and beyond, looking at nationalneeds in pure and applied nuclearscience, the production of new nuclearscientists, mentoring them on thevariety of post Ph.D. careers, and effortsto educate the public at large on issuesrelating to nuclear science.

RICHARD F. CASTEN

Chair, NSAC

Table 1. NSAC Activities—2003/2004

Charges (short titles) Chairs

Facilities Charlie Glashausser, RutgersFundamental NP with Neutrons Bob Tribble, TAMUNuclear Theory Berndt Mueller, DukeEducation Joe Cerny, U.C. Berkeley and LBNLPerformance Measures/ Milestones Don Geesaman, ANLCommittee of Visitors John Cameron, IndianaRIA/GSI Peter Bond, BNLRHI Peter Barnes, LANL

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Oldest Institute of the Austrian Academy of Sciences

Renamed as Stefan Meyer Institut für subatomare Physik

On 25 June 2004, the AustrianAcademy of Sciences decided torename its Institute for Medium EnergyPhysics as Stefan Meyer Institut fürsubatomare Physik. The former hadbeen the successor institute of thefamous “Institut für Radiumforschung,”which was founded in 1910 as theworld-wide first institute of its kind.Stefan Meyer was the first director.Based on a generous donation ofKarl Kupelwieser, the “Institut fürRadiumforschung” was at that time thefirst research institute of the then“Imperial Academy of Sciences.”

The renaming is connected to a newscientific direction, which was initiatedby the last director of the Institute forMedium Energy Physics and firstdirector of the Stefan Meyer Institut,Paul Kienle.

The Stefan Meyer Institut is doingresearch in the field of strong

interaction at low energy. It is involvedin several international collaborations.Presently, the Stefan Meyer Instituttakes part at experiments at the LNF,Laboratori Nazionali di Frascati in Italyand at the PSI, Paul Scherrer Institutein Switzerland. At the LNF it is memberof the DEAR collaboration, which isdevoted to the study of kaonichydrogen. An experiment, determiningthe strong interaction shift andwidth of the 2p-1s transition has

recently been concluded. Preparationsfor SIDDHARTA, the successorexperiment to DEAR are well underway. Its goal is the measurement of theground state shift and width due tostrong interaction in kaonic deuterium.

At PSI, the institute is part of thePionic Hydrogen Collaboration, whichaims at the measurement of thehadronic shift and width of pionichydrogen at the percent level.

In November 2004 EberhardWidmann was appointed director of theStefan Meyer Institut. He is head of thespectroscopy group of the ASACUSAcollaboration at CERN and con-sequently the institute is part of thiscollaboration.

In the future, the Stefan MeyerInstitut will be engaged at FAIR(Facility for Antiproton and IonResearch), the future project of the GSI,Darmstadt. This new line of researchtakes into account the changinglandscape of European nuclear andparticle physics. The FAIR project willresult in one of the biggest and mostcomplex accelerator facilities in theworld. The Stefan Meyer Institut plansto be part of several experiments atFAIR:

• At FLAIR (Facility for Low-energyToshimitsu Yamazaki, Pierre Radvanyi, Hélène Langevin-Joliot, Paul Kienle.

Logo of the Stefan Meyer Institutfür subatomare Physik

Logo of the Austrian Academyof Sciences

Antiproton and Ion Research),where a low energy antiproton beamat high intensity is used forspectroscopy of antiprotonic atomsamong other fields of research.Eberhard Widmann is spokespersonof the FLAIR project.

• At AIC (Antiproton-Ion-Collider),proposed by Paul Kienle to measurethe difference of neutron and protondensity distributions of nuclei far offstability by medium energyantiproton absorption.

• At PANDA (Antiproton Annihi-lation at Darmstadt) high energyantiprotons are extracted toinvestigate charmonium, glue-balls,hypernuclei, and other topics.

Stefan Meyer—Austrian Pioneer

of Nuclear and Particle Physics

Born in Vienna in 1872, StefanMeyer was one of the pioneers ofmodern nuclear and particle physics inAustria. He organized the constructionof the “Institut für Radiumforschung”in Vienna and headed this researchinstitute as its first director from 1910to 1938. In the early days of researchon radioactivity the then Austro-Hungarian monarchy was the onlysupplier of radium samples, due to itsmines in Joachimsthal, now part of theCzech republic. Together with MarieCurie and Ernest Rutherford, Stefan

Meyer, being secretary of theInternational Radium-Standard-Commission, played a crucial role inthe establishment of the so called“Radium standards.” His contributionto this ever growing field of physics waswidely recognized and appreciated andcumulated in his election as presidentof the International Radium-Standard-Commission. Forced to retire after the“Anschluss” of Austria to national-socialist Germany, Stefan Meyersurvived the horrors of the SecondWorld War in Bad Ischl. Unlike manyothers, he could return to Vienna to seethe reconstruction of his institute.Stefan Meyer died in 1948.

It was Stefan Meyer, who made LiseMeitner interested in the physics ofradioactivity. During his directorshipViktor Hess and Georg V. Hevesyworked at the institute, who becomeNobel laureates in 1936 and 1948,respectively. Viktor Hess, being StefanMeyer’s research assistant, discoveredcosmic rays during his balloon flights.Georg V. Hevesy, hearing about theexcellent experimentalists at theRadiuminstitut, came to Vienna toperform his first experiments on theradioactive tracer method.

By naming this institute after StefanMeyer, the Austrian Academy ofSciences is honoring one of its mostexcellent scientists.

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Festivity on the Occasion of the

Renaming of the Stefan Meyer

Institut

On the occasion of the renaming ofthe Stefan Meyer Institut für subatomarePhysik, festivities were held on 29October 2004. The names of StefanMeyer, together with Viktor Hess,Georg V. Hevesy, as well as MariettaBlau and Berta Karlik, were engravedin the institutes marble table of honors.At the premises of the AustrianAcademy of Sciences a symposium washeld to commemorate the institute’s newname. Among the many distinguishedspeakers, Hélène Langevin-Joliot,granddaughter of Marie Curie, andPierre Radvany gave a touchingpersonal account of their memories onthe early days of radioactivity researchand the most prominent persons.

Paul Kienle summarized the spiritof the day: “The Stefan Meyer InstituteI wish all the best for the future andsuccess in its scientific projects. Meetthe challenge of your demanding name!Standing in a tradition, create a newone!”

HERMANN FUHRMANN

Stefan Meyer Institutfür Subatomare Physik Austrian

Academy of SciencesMore information and photos are

found at: http://www.oeaw.ac.at/smi

2005March 13–20

Bormio, Italy. XLIII International

Winter Meetings on Nuclear Physics.

Contact: Prof. I. Iori, Bormio WinterMeeting, Dipartimento di Fisica, ViaCeloria 16, 20133 Milano, [email protected]

March 19–23

San Servolo, Italy. FUSION06,

International Conference on Reaction

Mechanisms and Nuclear Structure at

the Columb Barrier. Contact: LorenzoCorradi, Chair. [email protected]

Web: http://www.lnl.infn.it/~fusion06/

March 29–April 5

Kloster Banz, Germany. Neutron-

Rich Radioactive Ion Beams—

Physics with MAFF. Contact: R.Fischer, Dept. of Physik, UniversitätMünchen, Am Coulombwall 1, 85748Garching, Germany. Tel.: +49 89 28914078. E-mail: [email protected]

Web: http://www.ha.physik.uni-muenchen.de/maff/workshop

May 16–20

Debrecen, Hungary. Nuclear

Physics in Astrophysics - II.

Web: http://atomki.hu/~npa2/

May 16–22

Bonn, Germany. International

Conference on Low Energy

Antiproton Physics (LEAP-05).

Contact: Walter Oelert, Institut fürKernphysik, Forschungszentrum JülichGmbH, D-52425 Jülich, Germany. Tel.:+49 2461 61 4156. Fax: +49 2461 613930. E-mail: [email protected].

Web: http://www.gsi-bonn.de

May 23–26

Bonn, Germany. 6th International

Conference on Nuclear Physics at

Storage Rings STORI05.

Web: http://www.fz-juelich.de/ikp/stori05/

May 27–31

Aschaffenburg, Bavaria, Germany.

SHIM 2005: Swift Heavy Ions in

Matter. Contact: Stefanie Lüttges,Gesellschaft für Schwerionenforschung,Planckstr. 1, D-64291 Darmstadt, Tel.:+49 6159-71-2721; Fax: +49 6159-71-2134, [email protected]

Web: http://www.gsi.de/SHIM2005

June 14–18

Lund, Sweden. International

Conference on Finite Fermionic

Systems, Nilsson Model 50 Years.

Web: http://www.matfys.lth.se/Nilsson

June 20–25

Debrecen, Hungary. Exotic

Nuclear Systems (ENS ‘05).

Web: http://www.atomki.hu/ens05/

June 28–July 1

St. Petersburg, Russia. LV

International Meeting on Nuclear

Spectroscopy and Nuclear Structure.

Contact: Dr. A. Vlasnikov, Institute ofPhysics, St. Petersburg State University,Uljanovskaja Str., 1, Petrodvorets, St.Petersburg, Russia, 198504. E-mail:[email protected]

Web: nuclpcl.phys.spbu.ru/nuclconf

August 25–September 2

Mainz, Germany. Euro Summer

School on Exotic Beams. Contact: E-mail: [email protected]

August 30–September 6

Piaski, Poland. XXIX Mazurian

Lakes Conference on Physics:

“Nuclear Physics and the Funda-

mental Processes.

Web: http://zfjavs.fuw.edu.pl/mazurian/mazurian.html

calendar

September 4–9

Notre Dame, Indiana, USA. 12th

International Conference on Capture

Gamma-Ray Spectroscopy &

Related Topics. Contact: Prof. AniAprahamian, 225 Nieuwland ScienceHall, University of Notre Dame, IN46556-5670, USA. Fax: 574-631-5952.E-mail: [email protected]

Web: http://www.nd.edu/~nsl/cgs12/

September 5–9

Pavia, Italy. The XIX Nuclear

Physics Divisional Conference

(NPDC19) of the European Physical

Society.

Web: http://www.pv.infn.it/~npdc19

September 10–14

Zaragoza, Spain. Ninth Interna-

tional Conference on Topics in

Astroparticle and Underground

Physics (TAUP). Contact: TAUP 2005Secretariat, Ms. Mercedes Fatás,[email protected]

Web: http://www.unizar.es/taup2005

September 12–17

Kos, Greece. Frontiers in Nuclear

Structure, Astrophysics, and

Reactions Conference (FINUSTAR).

Contact: [email protected]: http://www.inp.demokritos.gr/~finustar

September 12–15

Caen, France. 11th International

Conference on Ion Sources ICIS05.

Web: http://www.ganil.fr/icis05

September 19–24

Milos, Greece. 6th Research

Conference on Electromagnetic

Interactions with Nucleons and

Nuclei (EINN 2005). Contact: PaulHoyer. Email: [email protected]

Web: http://www.iasa.gr/EINN_2005/EINN05/


October 3–7

Iguazú, Argentina. The Sixth

Latin American Symposium on

Nuclear Physics and Applications.

Contact: [email protected]: http://www.tandar.cnea.gov.ar/misc/SLAFNAP6.php

October 16–22

Dresden, Germany. Workshop on

Critical Stability. Contact: Aksel S.Jensen, [email protected] or LaurentWiesenfeld, [email protected].

Web: http://www.mpipks-dresden.mpg.de

calendar


November 23–25

Brussels, Belgium. 3rd

International Conference on

Education and Training in

Radiological Protection (ETRAP).

Contact: Dionne Bosma, ConferenceCoordinator, [email protected]

Web: http://www.etrap.net/

2006March 19–23

San Servolo, Italy. FUSION06,

International Conference on Reaction

Mechanisms and Nuclear Structure at

the Columb Barrier.

Web: http://www.lnl.infn.it/~fusion06/

September 2–6

Rio de Janeiro, Brasil.

International Conference on Nucleus-

Nucleus Collisions NN2006. Contact:[email protected]

More information in

the “Calendar” on

http://www.nupecc.org

nuclear physics - nupecc · calendar ... cover illustration: a photo of high energy accelerator...

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