The J-PARC Hypernuclear Physics Programs- Hyperonization in dense nuclear matter -Toshiyuki TakahashiIPNS, KEK

Contents Introduction of J-PARC Facility Hadron Hall Physics Programs PAC MeetingHypernuclear Physics at S=-2Hypernuclear Physics at S=-2Physics on Hadrons with StrangenessSummary

the Pacific OceanTokai VillageHitachinaka P.S.Tokai-2 Nuclear P.S.J-PARC

J-PARC FacilityLinac3GeV Rapid Cycling (25Hz) Synchrotron(1MW)50 GeV Synchrotron(0.75MW)Materials and Life Science FacilityJapan Accelerator Research ComplexNeutrino Beamline to Super-KamiokandeHadron Hall (Slow Extracted Beams)Joint Project between KEK and JAEA

Phase 1 & 2The budget for about 2/3 of the entire project has been approved by the Japanese government from JFY2001 as Phase 1.Phase 1 (~151 billion Yen) consists of major accelerator components and a part of experimental facilities.270 kW for slow extractionhalf size of Hadron Hall

JAEAKEK

Construction ScheduleCurrent

Hadron Hall

Hadron Hall Layout (Phase 1)ProductionTarget (T1)

K1.8(2009 Sep.)K1.8BR (2008 Dec.)K1.1K0.8KL(2010?)Primary beams

Secondary BeamlinesK1.8K1.8BRHigh intensity K- beams are available !!Kaon FactoryHigh-reslution beam spectrometer

Primary proton beam50 GeV-15mA30 GeV-9mALength (m)45.853Acceptance (msr.%) 1.4Max. momentum (GeV/c)~2.0K- intensity (ppp) @1.8 GeV/c6.6E+061.4E+06 @1.5 GeV/c2.7E+060.54E+06 @1.1 GeV/c0.38E+060.08E+06Electrostatic separator750kV/10cm, 6m2Single rate @ MS2 @ 1.8 GeV/c 33E+068E+06K-/(p-+m- ) @ FF @ 1.8 GeV/c 43.5X/Y(rms) size @ FF (mm)19.8 / 3.2

Primary proton beam50 GeV-15mA30 GeV-9mALength (m)27.573Acceptance (msr.%)2.5Max. momentum (GeV/c)~1.2K- intensity (ppp) @1.1GeV/c5.5E+061.2E+06 @0.8 GeV/c1.0E+060.2E+06 @0.6 GeV/c0.1E+060.02E+06Electrostatic separator500kV/10cm, 6mSingle rate@D3out @1.1 GeV/c 30E+06>7E+06K-/(p-+m- ) @ FF@1.1 GeV/c 10.9X/Y(rms) size @ FF (mm)5.9 / 2.9

Physics ProgramsPAC Meeting 1st Jun.31 Jul.2, 2006 2ndJan.10 Jan.12, 2007 3rdJul.6 Jul.7, 200717 Proposals & 7 LOIsStage-2 Aproval9 (5 Day-1 Experiment)Stage-1 Aproval6Deffered1Rejected1

Hypernuclear Physics at S=-2E07 Systematic Study of Double Strangeness Systems with an Emulsion-counter Hybrid MethodE05Spectroscopic Study of X-Hypernucleus, 12XBe, via the 12C(K-,K+) ReactionE03Measurement of X rays from X- Atom

Motivation to Study S=-2 SystemNew sector of Baryon-Baryon interaction LLweakly attractive XNattractive ? XN->LLVery dynamic systemSmall mass difference LL and XN (and H?)Significant step toward multi-strangess systems Core of neutron star ...

S=-2 SystemXN->LL couplingMixing effect is more significant in S=-2 system

Potential and Impact on Neutron StarsStrange baryons apear in the core of neutron star...What kind of baryons will apear ?At how much density will they apear?depend on mass, charge, interactionNegative baryons are favorable.reduce electron Fermi energy S- was supposed to be important. However its interaction with neutron matter is found to be strongly repulsive. X- and its interaction should be important.

How to produce and studyS=-2 systemsK- + p -> K+ + X- p(K-)~1.8GeV/cDirect productionReaction Spectroscopy(E05)Decay measurementsEmulsion (E07)X-rays Measurements(E03)

E07 Previous Studies on Double-Strangeness SystemsKEK-PS-E373 (1998 - )Weakly attractive LL interactionTwin hypernucleusX- (binding) energy at the absorbed pointX- Nucleus interaction

E07 Double L Hypernuclei expected ~100 events extend known species species dependence of DBLL decay form

H-dibaryon

X-Nucleus Interaction twin hypernuclei X-ray from atomic states

Unknown Phenomena

Systematic Study of Double Strangeness Systems with an Emulsion-counter Hybrid Method

# of absorbed X-# of LL-hypernuclei# of twin hypernuclei1965D. Davis4(expected)11987-1997(KEK-E176)80121998-present(KEK-E373)~8007 (1)3J-PARC E07~10000~10020-30?

E05 Previous Studies on X-Hypernucleus and X PotentialT.Fukuda et. al, PRC58(1998)1306P.Khaustov et al, PRC61(2000)0546KEK-E224(K-,K+) Missing Mass Spectroscopy on CBNL-E885DM=14MeVDM=22MeVEvidence !? V = -14 MeVinsufficient resolutionpoor statistics

E05Missing mass spectroscopy K1.8 Beam Spectrometer Dp/p=3.3x10-4(FWHM)SksPlus Spectrometer Dp/p=1.2x10-3(FWHM) ~30 msr

~3 MeV(FWHM) resolution

~190 bound events 1.6x106 /spill K- beams 1 month data-taking

Spectroscopic Study of X-Hypernucleus, 12XBe, via the 12C(K-,K+) Reactionexpected spectrumVX=-20MeVVX=-14MeVGX=1MeV

E03 X- Nuclues potentialReal partLevel energy shiftImaginary partWidthX ray yield Regardless of potential detailattractive / repulsivestrong / weak absorption Complementary to E05E03 surface region of the potentialE05 inner part of the potentialMeasurement of X rays from X- Atom

Hypernuclear Physics at S=-1E10Production of Neutron-rich Lambda-Hypernuclei with the Double Charge-exchange ReactionE13Gamma-ray Spectroscopy of Light HypernucleiE18Coincidence Measurement of the Weak Decay of 12LC and the Three-body Weak Interaction ProcessE22Exclusive Study of the Lambda-N Weak Interaction in A=4 Lambda-Hypernuclei

E10 Neutron-rich L Hypernuclei and DCX Reactionordinary nucleiNo Charge eXchange(p+,K+), (K-,p-)L hypernuclei

E10 Motivation LS coupling

important in n-rich hypernuclei L potential in n-rich enviroment strangeness contents in neutron starsChange of nuclear structureCore + LDeformed Core + LHypernucleus+ neutron halon-rich hypernucleus

E10 Produdution of N-rich HypernucleiTwo step reaction p-p->p0n, p0p->K+L p-p->K0L, K0p->K+LSmall cross section~10 nb/sr (10-3 of NCX)Need high intensity beam1x107 /spill p- beam pp=~1.2GeV/cNeed high resolution~2 MeV/c2(FWHM) with SKSYield estimate for 9LHe~300 events with 3 weeks KEK-E52110B(p-,K+)10LLi~45 events at bound regionNo backgound

Physics on Hadrons with StrangenessE15A Search for Deeply-Bound Kaonic Nuclear States by In-flight 3He(K-,n) ReactionE17Precision Spectroscopy of Kaonic 3He 3d->2p X-rays E19High-Resolution Search for Q+ Pentaquark in p+p->K+X Reaction

E15 Kaonic Nuclear States KpX Exp. (KEK) -> strongly atractive in K-p system L(1405) as a bound state of K- and p Kaonic nuclear states may exist.

contour plot of nucleon density distribution by AMDA.Dote et al., PRC70 (2004) 044313.rcenter = ~10 r0Ultra high density nuclear matter(c.f. core of neutron stars ) could be obtained !!T.Yamazaki and Y.Akaishi Phys. Lett. B535(2002) 70.glue-like role of K-

E15 Missing-Mass Spectroscopy and Invariant-Mass Spectroscopyn3He(K-,n)XMissing-mass spectroscopyK-nProductionDecayK-pp -> L p -> p p-@K1.8BR beamlineInvariant-massspectroscopyCDS in Solenoid Magnet

SummaryThe construction of J-PARC facility will be completed and its operation will start soon. MR operation2008 MayFirst beam to Hadron Hall2008 Dec.K1.8BR 2008 Dec.K1.82009 Sep. Hadron facility is Kaon Factory.1.4 x 106 K-/spill, K-/(p- + m-)=3.5@1.8GeV/c@K1.81.2 x 106 K-/spillK-/(p- + m-)=0.9@1.1GeV/c@K1.8BRA lot of physics programs on hypernuclear & strangeness physics are waiting the beam.Research on S=-2 system is main subject among them

Backup

J-PARC PAC System and Beamtime ChargePAC for Particle & Nuclear ProposalsPAC for Materials & Life ProposalsBeamtime Charge

Commissioning & Linac Energy RecoveryConstruction needs to start from JFY2008, hopefully for 3 years, as shown in this figure.Issue and Concern:This budget plan has not been included in the current plan at JAEA.JFY2008 JFY2009 JFY2010 JFY2011 JFY2012JFY2013Phase 1Completion

Cost Analysis for Operational Budget

UX , GX and Partial Wave Contributions in Nuclear MatterOBE (NHC-D, Ehime) no t-channel meson exchange odd-state attraction strong A-dependence of VX small width(MeV)ESC04d* strong attraction of 3S1(T=0) large width

ModelT1S03S11P13P03P13P2UXGXNHC-D01-2.6-3.20.1-2.3-2.1-3.0-0.2-0.0-0.7-3.1-1.9-6.3-25.20.9Ehime01-0.9-1.3-0.5-8.6-1.0-0.80.3-0.4-2.4-1.7-0.7-4.2-22.30.5ESC04d*016.37.2-18.4-1.71.2-0.81.5-0.5-1.3-1.2-1.9-2.8-12.112.7

Selection of targetsPhysics view: Batty et al. PRC59(1999)295For given state, there is optimal targetNuclear absorption is reasonably smallX-ray energy shift and width are the largest (~1 keV)They suggested 9F, 17Cl, 53I, and 82Pb for n=3,4,7,9.

The choice depends on the optical potential itself We cant know before the 1st experiment

n:435465768798109F(Z=9)Cl(17)??I(53)?Pb(82)131 (keV)223??475?558

n:435465768798109F(Z=9)Cl(17)Co(27)?Y(39)?I(53)Ho(67)?Pb(82)131 (keV)223314?394?475518?558

For the 1st experimentWe chose Fe (Iron) because of (mostly) experimental reasonProduction rate: A-0.62 as cross section scales with A0.38Stopping probability: requires high target density (X- range: 10-20 g/cm2, bgct ~ 2cm)X-ray absorption: significant at large Z Small Z(A), yet high densityKoike calculated the energy shift (width) & yield of the Fe X ray (n=6 5)Woods-Saxon potential: -24 - 3i MeVEnergy shift: 4.4 keV, width: 3.9 keVYield per stopped X-: 0.1 (~0.4 without absorption)

Yield & sensitivity estimationTotal number of K-: 1.0x1012 for 100 shifts.Yield of Xproduction:3.7106stopped: 7.5105X-ray yield2500 for n=65 transition7200 for n=76 Expected sensitivityEnergy shift: ~0.05 keV (systematic dominant) Good for expected shift (~1 keV, 4.4 keV by Koike ) < 5% accuracy for optical potential depthWidth: directly measurable down to ~ 1 keVX-ray yield gives additional (indirect) information on absorption potential.

Expected X-ray spectrumn= 65

shift & width0 keV

Expected X-ray spectrum(2)n= 65

shift & width4 keV

Exotic L-hypernucleiExample of hydrogen5LH No evidence6LH Stable ?7LH Stable ?Super Heavy HydrogenHyper Heavy HydrogenWe can produce at J-PARC

Requirement: Resolution (1)Clear identification of hypernucleiBinding energy (guess) : 9LHe ~8MeV, 6LH ~3MeVStrong quasi-free L-production backgroundIn the case of 6LH hypernucleusEnergy resolution 2.5MeV (FWHM)

Production cross section4LHe(g.s., 0+) productionestimation with DWIA by T. Harada

First of all, I would like to thank the organizer to give me an oppotunity to present here.I will talk about The J-PARC Hypernuclear Physics programs

This is the contents of my talk.First of all, I breafly show J-PARC project and facilities as a introduction,Especially hadron hall facility is shown.Next various physics experiments concerning to hypernuclear and strangeness physics are shortly introduced.Finally Ill summarize my talk.

This is an aerial photograph of our J-PARC site.J-PARC is located at Tokai-Village facing the Pacific Ocean.

J-PARC means Japan Accelrator Reseach Complex.which consists of Linac, 3GeV rapid cycling Syncroton, and 50GeV Main Synchrotron.The sales point of J-PARC is high-beam-power accelerator.Beam-power, namely, beam energy times intensity, are 1Mega-Watt for RCS, and 0.75MW for Main Synchroton.

Three are three experimental faciliesMaterials and Life Science Faciliy which uses beam from 3GeV RCS.Neutriono beamline to Super-Kamiokande with fast extracted beamsand Hadron hall facility which uses slow extracted beam from MR.

J-PARC is joint project between KEK and JAEA.

The project is devided into two pahses.The budget for about two-third of the enitre project has been apporved as Phase 1.Phase 1 consists of major accelerator components and a part of exprimental faciilies.Therefore, unfortunately, beam power is limited to 270kW for slow exstracted beam andthe size of Hadron hall is about half of the original plan.

This table shows construction scheule.The project started in 2001. Now is here.For LINAC, beam acceleration was already suceeded in last fiscal year.From this autumn, beam commissioning of 3GeV RCS will start.Next year, beam commissioning of MR will start andFirst beam will come to Hadron Hall in December.Neutrino beam will be available April, 2009.

This picture show hadron hall.The constraction of the building was recently completed.

This figure shows schematic view of hadron hall at Phase 1.

This is the primary beamline. Primary proton from MR hits the production target here and generates various sencondary particles such as kaons, pions.At the left side, charged kaon beamlines, K1.8 and K1.8BR will be constructed.At the right side, another charged kaon beamline, K1.1 and K0.8 is planned.And neutral kaon line will be constructed. There are reseaved space to build the primary beamline.We can perform the experiements which use the primary beams even in Phase 1 period.

Because of the limited construction budget, only a few beamlines are availableat the very early stage of the beam operation.

K1.8BR, the upstream of K1.8, will be ready at December 2008. K1.8 full beamline will be ready at September 2009.

These tables show the performance of K1.8 and K1.8BR beamlines.K1.8 beamline was designed and optimazed to preform the spectroscopy of S=-2.Maximum momentum of K1.8 beamline is 2 GeV/c, suitable forCascade particle production.It has two stage of the electro-static separators, thus high purity charged kaon beam of K/pi is about 4 can be obtained.At the end of the beamline, a high-reslution beam spectrometer will beequipped.

On the ohter handK1.8BR beamline, which is a upstream part of K1.8, also providesgood kaon beam of 1.1 GeV/c.

K- beam of the intensity around tenth-six / spill can be obtained evenat Phase 1,When the MR energy and intensity are upgraded at Phase 2 project,5 times higher intense beam can be obtained.This is the Kaon Factory.

To sellect physics programs,PAC meetings were held three times upto now.

17 Proposals and 7 LOI were submitted and discussed in these PAC Meetings.As a results, 9 Proposals got stage-2 aproval. Among them 5 experiments were sellected as Day-1 experiment.6 proprosal got stage-1 appoval.

This list summaried the status of the proposals.

3 proposals convcerning to hypernuclear physics at S=-2 system.

4 proposals are hypernuclear physics at S=-1 system.

And three proposals are related Hadron and Hadron systems with StrangenessFirst categoly is Hypernuclear Physics at S=-2 systemThese three experiments are categolized in this thema.

Fist of all, motivation to study S=-2 system is breifly summaried here.One of the purpoeses for hypernuclear physics is to understandnuclear force like N-N interaction by extending to strangeness degree of freedom.Extended baryon baryon interaction should be understodd in the framework of flavor SU(3).In this point of view, S=-2 system is new sector of B-B interaction.Lambda-Lambda, Xi-N, and Xi-N going to LL conversion are subject to know.Lambda Lambda interaction was found to be weakly attractive from the recentdouble-Lambda-hypernucleus data.However for others, little is known so far.

Secondary, S=-2 system is very dynamic system.Since mass difference between LL and XiN or even H-particle is very small.these states may couple and may be mixed each other.

Finally, it it significant step toward multi-strangeness systemswhich is believed to appear in high density nuclear mattersuch as core of neutron stars.

In non-strangeness world, mass difference betwenn Nucleon and Delta is 300 MeV,sometimes delta contribution is discussed.At S=-1 world mass difference between Lambda and Sigma is 75 MeV,theoritical calculation shows contirbution of Lambda-SIgma mixing is a few % in lighthypernuclei, In the case of S=-2, mass difference is only 30MeV, there large mixing effects areexpected.

Concering to Cascade system, The potential may give an impact on Neutron stars.

Many theories predict that strange baryons will apear in the core of neutron star.But , what kind of baryons, at how much density will pear?These questions, off cource, denpend on baryon mass, charge, and details of the interaction.

In general negative baryons are favorable because it can reduce electron Fermi energy.So Sigma-, the lightest negative charged baryon, was supposed to be iomportant for a long time.However its interaction with neutron matter is found to be strongly repulsive.Therefer Xi-, next lightest baryon, and its interaction should be important.

S=-2 system will be produced using (K-,K+) reaction.Produced Xi- will absorbed by other nuclei.A very small percent of these processes, X- is trapped by the same nucleus, namely, direct productionReaction spectroscopy will observe this direct production process.

In the absorption process, Xi- forms Xi-Atom and emiting X-rays,E03 measures these X rays.

Formed S=-2 system will anyhow, decay.Emulsion experiment measures these decay processes.

The cross section of the elementary process shows the peak at around 1.8GeV/c. Therefore, 1.8GeV/c K- beam is used

The highlight of the previous studies by Emulsion is so-called Nagara-Event which was foundat E373 Experiment.This event was uniquely interpreted as a Helimu-6-double-Lambda.Mass, Binding energy, thus, interaction energy between 2 lambdas, deltaBLambdaLambdawere obtained.From this event, LL interaction is found to be weakly attractive.

In the same experiment, several twin hypernucleus events were found.These events give the information of Xi- Nucleaus interaction.

This is the schematic drawing of the setup.Xi- is produced by (K-, K+) reaction on diamond target and stops in the emulsion stack.These reactions are tagged by the spetrometer system and Xi track is measured by Double-sided silicon-strip detectors located up- and downstram of the emulsion stack.And decay pattern of double strangeness system will be searched in the emulsion by guiding these counter information.

This table sumarieze the history of search of double strangeness system.In the pionner work by Davis, one double-lambda event was found in totally4 Cascade absorbed events.In the first emulsion-counter hybrid experiment, E176,There were 80 absoption events and one double Lambda was found.Next generation experiment, E373, 800 Xi were absorbed, and 7 event were found.Among them, one event was uniqiely interpleted as I tald.

J-PARC expriment aims to accumulate 10-thousand absobed events.We expepect about 100 double-Lambda events and extend known hypernuclear pecies,and measure mass dependence of DeltaBLambdaLamda and Decay form.H-dibaryon and Xi-Nucleus potential are also subjects of the experiment

Concernling to Cascade hypernuclei,(K-, K+) missing mass spectroscopy on Carbon target were performedpreviously, KEK-E224 and BNL-E885.Although the peak structure was not observed due to insufficinet experimental resultion,they claimed that there is the yield in the bound region.Spectrum shape analysis showed Potentail depth is -14 MeV

The existense of the Xi-Hypernuclear states is not conclusive now,since the experimental resution and also statistics were not enoungh.

Therefore, we will perform such a spectroscopy at J-PARCwith much improved resolution and statistics.K1.8 beamline has high-resolution beam spectrometer of the resolution of ...Scatteed K+ will be detected SksPlus Spectrometer, which will be constructedby adding an dipole magnet in front of the existing SKS magnet.

We expect overall reslution of about 3 MeV andabout 200 bound events using full intenisty of Phase.1 and 1 month data-taking.This is the expected spectrum.

E03 measure X-rays from Cascede-Atoms by using Germanum detector array.Xi- atomic levels are modified by the influlence of the strong interaction, namely, Xi Nucleus optimal potential.Real part of the potential can be obtained from the level energy shift.Imaginary part can be obtained from the width of state and X-ray yield.

Regardless of potential detail, attractive or repulsive, strong or weak absorption,this method is applicable.This is the great advantage of this experiment.

I emphasized here that this experiment is complementay to E05.From E03, the surface region of the potential is obtained.On the other hand, E05 is sensetive to the inner part of the potential.

Next Ill go on hypernuclear physics at S=-1Among 4 proposal, I here show E10.

One of the ohters is gamma-ray spectroscopy to measure gamma-ray from hypernuclei by the Germinium array detector.Other two proposals are Weak decay of Lambda-Hypernucleus, which related to Baryon-Baryon Weak interaction.

E10 is the spectrosopy of Neutron-rich Lambda-Hypernuclei.Previouslly most of the spectrosopy experiments used No Charge exchange reaction such as (pi+,K+) or (K-,pi-)Produced hypernuclei are limited to near N equal Z hypernuclei.

If we used double charge exchange reactions such as (pi-,K+) or (K-, pi+),neutron-rich hypernuclei can be produced.

We have already performed such experiment using (pi-,K+) reaction on Bolon-10 target producing Lithium-10-Lambda.At J-PARC we are going to produce Hydrogen-6-Lambda and Helium-9-Lambda hypernuclei. Motivations of E10 are followings,One is Lambda-Sigma couping or mixing.(As previously mentioned this mixing effects may contrubute a few % in light hypernuclear system)

This transition interaction is forbitten between isospin zero nuclei.And between lambda-hypernucleus and excited sigma-hypernculeus is energically suppressed.Therefere this couping effect is more important in neutron-rich hypernuclei.

Secondly, Lambda effective potential in n-rich envirment may be changed though such Lamda-Sigmacoupling interaction. This may affect the strangeness contents in neutran stars.

Finally, interest of change of nuclear structure.Neutron rich hypernucleus may have such a exotic structureof hypernucleus core plus neutron halo.

Left figure is Lithium-10-Lambda spectrum measured in KEK-expriment.We obsearved 45 events at bound region.

Since this reaction is two step reaction, cross section is very small.10 nb/sr which is three-oder of smaller than NCX.To compensate to small cross section high intensity beam is necessary.High resolution is also required.We will use tenth-seven /spill pion beam at K1.8 beamline andthe SKS spectrometer.3-hundred event are expected with 3 weeks data-taking for Helium-9-Lamda.

Final Topics arePhysics on Hadrons and Hadron systems with Strangeness.There are three expeiement.I show here E15,...

This experiment is search of kaonic nuclei or kaonoic nuclear states.

KpX experiment which measured X-rays from K- proton system.suggests strong attraction between K- and proton.Yamazaki, and Akaishi took Lambda(1405) as a bound state of K- and protonand calculate K-pp and K-ppn systemThey concluded that kaonic nuclear states may exist if K-p atraction is strong enough.Due to the glue-like role of K-, these system is shrunk.

This is the results of AMD calculation by Dote.ppn and ppn plus K-, and ppp plus K-.The density becomes 10-times as high as normal nuclear density.This is ultra high density nuclear matter such as core of neutron stars.

Therefore confirmation of such states and study of the propetry of such statesis very interesting and important.

This experiment performs missing mass spectroscopy as well as invariant mass spectroscoy in coincidense.(K-, n) reaction on 3He target are measured by beam spectrometer and neutron counter system,this is missing mass spectroscopy,Produced K- p p system will decays.Decay products will be mesured Cylindrical Detector system in Solenoid field surrounding the target region.

Ill summaried my talk.

This table shows Cascade Potential Depth and width in Nuclear Matter and Partial wave contributionusing three different baryon-baryon interaction modelThese three models give the atractive potential, but ther are very different in partial wave components.

In one boson exchange potential models such as Nijmegen Hard Core D or Ehime models,total atraction comes from Odd-state ataction, which gives strong A-dependence of Cascade-Nuculeus Potential.On the other hand, recent Nijmegen model ESC04d has strong atraction in triplet S-one (T=0) state;this is the origin of total atractive potential.For width, OBE predict very small width, while ESC04d predicts large width.