newsletter issue 11 - institute of physics...iop hepp group newsletter: issue 11 november 2011...

IOP HEPP GROUP NEWSLETTER: ISSUE 11 NOVEMBER 2011

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NewsletterIssue 11

What's Inside:

Report From our Chairman

The End of the Tevatron Era – Prof. Mark Lancaster. After 26 years we wave goodbye to the Tevatron. Having worked on the CDF experiment since 1996, Mark takes us on a journey through the life of the Tevatron.

Cosmic ray detectors for schools, and the STFC masterclass roadshow project

IOP Half Day Report

The student conference fund

Farewell to the Tevatron 28 years 1983–2011


IoP HEPP Group Chairperson’s Report

by Prof. Mark Lancaster

I am delighted to take over as the new chair of the HEPP group and I’d like to thank Phil Allport for all the hard work, tireless campaigning and commitment he has shown to the IoP HEPP group over the past three years. Much of the chair’s work goes unnoticed, but without it the standing of our subject within and outside the IoP would be severely diminished and Phil has done a magnifi-cent job. He is going to be a difficult act to follow.

The 10 months since the last newsletter have been a very exciting one for the field with more smoking gun signals of new physics than at any time I can remember, but at time of writing there is, alas, no confirmed sighting of the death of the Standard Model.

The LHC has gone from strength to strength, surpass-ing many people’s expecta-tion with its performance. Over 5 fb-1 of integrated lu-minosity will have been de-livered before the switch to heavy-ion running in early November and the peak lu-minosity is now ten times higher than achieved at the Tevatron.

The surprise to many is that none of the plethora of new phenomena predicted at the LHC have yet materialized. CMS/ATLAS has excluded heavy W bosons, excited quarks to ~ 2 TeV and evi-dence of extra dimensions (micro black holes) to ~ 4 TeV and LHCb has as yet found no enhancement in rare b-decays or CP viola-tion. The SUSY 2011 confer-ence was the scene of much introspection. The 1993 New York Times headline “315 Physicists report failure in search for SuperSymmetry” in the context of CDF has



thankfully been updated, not with mention of the “failure” of 7,000 physicists, but with the 2011 BBC headline “LHC results put SuperSymmetry theory ‘on the spot’”. This prompted Guido Altarelli to remark "It is not time to be desperate yet… but maybe it is time for depression”. Sig-nificant parts of SuperSym-metry parameter space have been probed and found to be barren thereby excluding sparticle masses in the range 0.2-4 TeV. The Higgs boson remains elusive to the end. The latest LHC results have ruled out a Higgs boson more massive than 145 GeV such that if it exists its mass is now restricted to a narrow 30 GeV mass window above 115 GeV. This however also coin-cides with the most probable mass region from the fits to electroweak data. The next 6 months promise to be very exciting. First hints of a low mass Higgs will emerge or the death knell will get louder. If the Higgs doesn’t

exist then 95% exclusions will be possible over the en-tire mass range favoured by the Standard Model in the next 6 months from the Teva-tron and LHC analyses. One way or another the Higgs saga will be resolved quickly.

While the LHC has not ob-served any new physics, anomalies on the edge of dis-proving the Standard Model abound. Proving the adage that 99.7% of all 3 sigma ef-fects occur at the end of an experiment, the Tevatron has produced a number of recent curiosities. CDF observed a 4.1σ excess in dijets pro-duced in association with a W boson, not observed by D0, observed a 3.4σ anomaly in the angular distribution of top quark pairs, and D0 has observed a 3.9σ discrepancy in the charge asymmetry of like-sign dimuon events from semileptonic b-decays. Sadly after 28 years of operation the Tevatron had its last col-lisions on Sep 30 (see subse-



quent article) but there is still much to come from both CDF and D0 who will inves-tigate the above anomalies with the full datasets and will have one last shot at the Higgs in the mass region be-low 130 GeV.

Outside of the collider world there has been similarly in-triguing results from the as-tro-particle, dark matter and neutrino communities. The long standing DAMA/LIBRA result with an annual modula-tion in event rate consistent with elastically scattering dark matter, that was also ob-served in the 2010 analysis from the CoGeNT collabora-tion, albeit with a much lower significance (2.7 sigma), hint at dark matter particles with a mass in the range of 5-12 GeV. Further grist to the mill came this summer with re-sults from CRESST-II who observed an excess of 67 events, again consistent with a low mass (10-20 GeV) dark matter particle interaction.

However the evidence is not yet incontrovertible since neither the XENON100, CDMS-II or EDELWEISS-II experiments have seen a sim-ilar rate of excess events and indeed have set cross section limits lower than implied by the DAMA/CoGeNT/CRESST results (see figure 1).

Fig.1 : Dark matter (WIMP) search results expressed in terms of cross section limits (or measure-ments) and the WIMP mass.

Not to be outdone by protons at the LHC and the cosmo-genic WIMPS, the plucky neutrino has delivered its fair share of interesting results. In



June T2K presented the first direct hints of a muon to elec-tron neutrino oscillation and measured a non-zero mixing angle (θ13) from 6 events when 1.5 events were ex-pected. The J-PARC complex was hit by the tragic earth-quake and tsunami in Japan, thankfully without loss of life, and the past 6 months have been spent recovering the complex. It is hoped that beams will circulate again be-fore the end of the year and T2K will resume data taking in 2012. If the T2K result is confirmed with higher statis-tics it will be a boon to the field. The much sought-after small differences in oscilla-tion between neutrinos and anti-neutrinos which one hopes will shed light on the universe’s matter anti-matter asymmetry would be some-what easier to measure with the large value of θ13 implied by the T2K results. The re-sults from the reactor experi-ments: Double-Chooz, Daya Bay and RENO which mea-

sure θ13 in a complementary way are eagerly awaited.

Arguably the most surprising announcement of the year came from the OPERA col-laboration who presented a result of the time of flight of neutrinos between CERN and Gran Sasso that could be in-terpreted as evidence of faster than light travel. The result received much press coverage with UK physicists at the forefront of the com-mentary. The result is under-going much scrutiny and the MINOS collaboration is ex-pected to make the same measurement in the next 6-12 months. If confirmed this would prompt a number of prominent physicists to eat hats and underwear on live TV.

The results of the govern-ment’s comprehensive spending review were re-leased this time last year. While many had feared a worse outcome for science,



the settlement for STFC still presents significant chal-lenges. The ring-fencing of international subscriptions was a very welcome an-nouncement but the flat-cash STFC budget effectively means a reduction of 15% over the next 4 years with a significant squeeze (more than 50%) in the capital allo-cation. The latter will make it very difficult for significant new projects to be undertaken exacerbating the reduction in breadth in the UK programme imposed as a result of budget pressures from the 2007 CSR. The CSR settlement was un-doubtedly helped by the vig-orous campaigning for sci-ence and HEP over the sum-mer of 2010. Learning lessons from the past we should however be mindful to keep the campaign going in “good” (well not absolutely woeful) times as well as bad. The press are eager to publish stories about particle physics both in terms of its science and benefits and I'd urge ev-

eryone to keep the pressure on. We should not forget that the number of HEPP RAs will have almost halved over the period 2005-2015. How-ever despite these funding problems the UK continues to punch above its weight in international comparisons. A soon to be published IoP in-ternational bibliometric benchmarking study places UK HEPP 2nd in the world in terms of field normalized ci-tation impact (nci). This is also illustrated by the signifi-cant leadership positions we have with UK physicists act-ing as spokespersons of T2K, SuperNEMO and MINOS and both the CMS and AT-LAS upgrade projects being led by UK physicists.

In taxing leadership roles, John Womersley, a former D0 spokesperson, has just been appointed as the new CEO of STFC. Congratula-tions to John and the IoP committee looks forward to working with John to make



the best case for our science. We wish him all the best and one hopes a smoother start than Paulo Di Canio has en-joyed down the road.

The annual conference in 2010 was a divisional one held in Glasgow in April and was a great success with over 400 attendees. We owe a big vote of thanks to our col-leagues in Glasgow for a stimulating and enjoyable conference. The annual con-ference in 2012 will be held at QMUL from April 2-4 and will be joint with the IoP as-tro-particle group. I look for-ward to seeing many of you there.

The End of the Tevatron Era

At 2:30PM on Sep 30 the last Tevatron collisions were recorded by D0 bringing to an end a collider that was en-visaged as early as 1970 and which provided high energy beams over a 28 year period.The Tevatron was the first high energy superconducting accelerator paving the way for the LHC and a host of other superconducting appli-cations. The Nobel laureate Leon Lederman rather the-atrically described supercon-ductivity as “the elixir to re-juvenate accelerators and open new vistas to the future”. The choice of super-conducting magnets allowed Fermilab to save $14M (in 2011 prices) in annual elec-



tricity costs and to double the energy of its existing acceler-ator, the imaginatively named “Main Ring”, whilst using the same tunnel. The Tevatron’s original moniker “The (En-ergy) Doubler” soon became “The (Energy) Saver” when the oil-crisis of the 1970s took hold and financial pru-dence became the byword. It only became known as the Tevatron in 1984 when the project’s success was assured.The decision to use supercon-ducting magnets was a brave one since nobody had built them on the scale (~ 1000) re-quired for the 6.3 km circum-ference accelerator. CERN after much deliberation opted for conventional magnets for the SPS thereby allowing UA1/2 to discover the W and Z bosons in 1983 while the Tevatron was still being com-missioned. The issue then, as now, was how to construct and train the magnets so they wouldn’t quench frequently and how to mass produce them to a precise specifica-

tion. A key innovation came from the Rutherford labs as part of the SPS supercon-ducting R&D work: the “Rutherford cable”, a novel winding of the superconduct-ing fibers into a cable that helped prevent quenches. The second bold step (not followed by superconducting competitors at Brookhaven) was to produce hundreds of magnet prototypes with only one design parameter changed at a time in the spirit of the Manhattan project thereby honing in on the opti-mum design. This painstak-ing prototyping work was led by Alvin Tollestrup who later became the founder of CDF. In 1979 after 3 years of test-ing, many loud quenches and frequent hurried dashes for emergency exits, Fermilab had a 21-foot magnet design that worked. The subsequent attention to detail in the minutiae of the production process allowed mass pro-duction to commence shortly after. At the peak of magnet



construction, 95% of the world’s superconducting ma-terial was in Fermilab and led the CEO of the world’s largest company supplying superconducting alloys, Robert Marsh, to remark: “Every program in super-conductivity that there is to-day owes itself in some mea-sure to the fact that Fermilab built the Tevatron and it worked.” In the current cli-mate where government funding demands “impact” this serves as an example of how the desire to answer a difficult and arcane scientific question prompts a com-pletely unforeseen technology to be advanced way beyond expectation to the benefit of millions. Prior to the Teva-tron, superconducting mag-nets were prohibitively ex-pensive and unreliable, after-wards they could be mass produced for the MRI hospi-tal market.

The superconducting magnets were only part of the Teva-

tron’s success. The cryogenic facility assembled to cool the magnets to 4.3K was, in 1983, the world’s largest cryogenic cooling system ever built, with a cooling ca-pacity of 23 kW delivering 5,000l/hr of liquid helium to the magnets. The facility was much copied and designated as a historic mechanical engi-neering landmark in 1993 and the Tevatron itself was recognized as one of the top 10 engineering achievements of the 20th century. A second challenge was to produce and accelerate anti-protons to an intensity ten times that of the SPS. This relied heavily on the stochastic cooling tech-nique developed for the SPS but was augmented with a lithium lens for focusing and collecting anti-protons into a bespoke accumulator ring. In 2005, having reached the limits with stochastic cool-ing, the successful imple-mentation of electron-cooling using the world’s highest power DC beam allowed the



anti-proton intensity to be further increased by a factor of 3 and was one of the key factors in the Tevatron ulti-mately delivering over 11 fb-1

of integrated luminosity.

Fig 2 : CDF event display from 1985.

The Tevatron lost the race to the W and Z but by achieving an energy triple that of SPS energy and a luminosity ten times higher (just as the LHC has now accomplished in lap-ping the Tevatron) the Teva-tron opened up a new win-dow on TeV-scale phenom-ena. CDF saw a handful of collisions in 1985 (at 1.6 TeV) and completed its de-tector for 1.8 TeV collisions (Run-0) in 1988 about a year before collisions began at LEP and SLC. For a brief

time in 1989 CDF had the world’s most precise mea-surement of the Z mass and by 1992 it had placed a lower bound on the top mass of 91 GeV at a time when the elec-troweak fits were predicting a mass of ~ 160 GeV and thus a long road to discovery. The D0 detector was com-pleted in 1992 and Tevatron Run-1 began in October 1992 by which point the CDF de-tector had been upgraded to include a silicon vertex de-tector to optimize its sensitiv-ity to the top quark. It would be another three years but fi-nally CDF/D0 announced the discovery of the top quark in March 1995 from a data sam-ple of 67/50pb-1. The mass agreed perfectly with that predicted from the elec-troweak data leading many at LEP to claim they had dis-covered the top quark ! A claim that would be disputed by the thousands of people who worked for twenty years from 1975 to make the Teva-tron and then CDF/D0 a real-



ity. The ensuing publicity just as the world-wide-web was taking hold was a precursor of what was to come with the LHC, but thankfully without leaks to a blog.

The discovery of the top quark is the most famous of the Tevatron’s discoveries but there have been many others. From 1983-1999 when the Tevatron wasn’t running in collider mode for CDF/D0 it ran in fixed-target mode for a variety of kaon, hyperon, neutrino and muon experiments. This programme produced over 300 papers in-cluding the first observation of direct CP violation in the kaon sector (kTeV experi-ment: 1999) and the discov-ery of the tau neutrino (DONuT experiment: 2000) as well as a host of QCD measurements that did much to establish QCD as the de-finitive theory of the strong interaction. The successful operation of the world’s first silicon microvertex detector

in 1985 in the E691 charm experiment revolutionized heavy quark physics, while other detector technologies: TRD, RICH, bespoke ASICs were also pioneered by the fixed-target experiments.

The Tevatron was upgraded in 1996-2001 with the aim of delivering a dataset of 2 fb-1. Thanks to many incremental improvements in the acceler-ator chain it was able to ex-ceed this by a factor of 6 – delivering a peak luminosity of 4x1032 cm-2s-1 and almost 12 fb-1 of integrated luminos-ity. Upgrades to the CDF and D0 detectors e.g. a silicon tracker for D0 and triggers e.g. a displaced-vertex hard-ware trigger in CDF led to the SM being probed to an unprecedented level over a wide energy range. The top quark mass has now been measured to better than 1 GeV and the W mass to 30 MeV (and soon below 20 MeV) which together place the tightest constraints on the



mass of the Higgs boson. Several SM firsts were ob-served, notably the observa-tion of single top production and the landmark observation of BS oscillations not to mention the discovery of six b baryon states. But the programme is far from over.

Fig 3 : The Headlines that her-alded the discovery of the top quark at the Tevatron in 1995.

Over 50 papers have been published this year alone and as was noted in the chair’s re-port there are a number of in-triguing results that will be

re-visited with the full dataset and the Tevatron still has the edge over the LHC experiments in sensitivity to a Higgs boson in the favoured low mass region be-low 120 GeV.

The UK joined the Tevatron experiments in 1998 (CDF) and 1999 (D0). The £5M (excl.-salary) investment over 12 years has been excel-lent value for money. Over 500 Run-2 papers have been produced with UK physicists at one time or another lead-ing every one of the physics sub-groups and providing three D0 spokespeople. The UK continues to lead analy-ses in the Higgs searches, top quark properties, W mass, Z properties and CP b-viola-tion.

If particle physics success was only measured in parti-cle discoveries then the Tevatron’s place in history is already assured. It has dis-covered 6 new b-baryon states and 2 fundamental



fermions. But its lasting legacy may well be the methodology to do precision physics at a hadron collider. In 1985 or even 1995 nobody would have believed that SM processes with cross sections of 1pb could be probed at the Tevatron or that BS oscilla-tions could be observed or there would be any sensitivity to the Higgs boson. But through ingenuity, hard-work, superb detectors and a won-derful accelerator this has been achieved and much of this methodology is now in harness at the LHC. The Tevatron has helped to estab-lish the Standard Model as the definitive theory of sub-TeV fundamental particle in-teractions. One can only hope that the LHC standing on the shoulder of the Tevatron will knock the SM from its pedestal.

A celebration of the UK’s in-volvement at the Tevatron and a forward look to the fi-nal analyses will take place at

a ½ day IoP meeting at Man-chester on the afternoon of 11/11/11 and I hope many of you will be able to attend. I will be buying pints after-wards!

Prof. Mark Lancaster

Particle Physics Masterclass Roadshows

copyright STFC

The Particle Physics master-class programme has been an enormous success over the past decade, with almost all of the UK’s HEP groups run-



ning an annual event, most of which are heavily oversub-scribed. In addition, there is an expanding international programme covering many European countries and the USA.

At present the demand from schools for masterclass places greatly exceeds the supply, and many schools which ap-ply for places must be turned away. In addition, many UK schools cannot participate simply because they do not have a University with a HEP group within easy reach.

STFC is attempting to ad-dress these limitations by complementing the existing program with a series of Mas-terclass Roadshows, which will take the full masterclass experience to areas of the UK which are not close to a Uni-versity-based masterclass. Obvious regions which fall into this category are North-ern Ireland, the Highland and Islands of Scotland, Devon

and Cornwall, and much of Wales. However, many schools find even modest dis-tances to be a serious barrier to participation, which means that significant areas of East-ern England would also ben-efit from a locally-based Masterclass.

The first Roadshow event will take place at Queens University Belfast, with the enthusiastic help of Prof Alan Fitzsimmons and his colleagues. Up to 100 A-level students from Northern Irish schools will visit the University on 13 January 2012 for a full day of lec-tures, a hands-on analysis ex-ercise using LHC data, and the chance to discuss all as-pects of particle physics with active researchers.

In order to turn this concept into a regular series of events, the support of the HEP community will be vital, especially in order to recruit a group of volunteer lectur-



ers who are able to travel to a small number of Road-shows each year. For more information, please contact Bruce Kennedy at ([email protected]).

by Bruce Kennedy (RAL/STFC PP & NP outreach

Officer)

Cosmic Ray Detectors for Schools

The idea of using cosmic ray detectors to enhance physics education in schools has re-cently taken off in Europe and North America, and was the subject of a workshop held at CERN in October 2010). Many countries al-ready have networks of detec-tors installed and operating in schools.

Plans are under way to de-velop a national cosmic ray detector network that in-cludes all interested parties in the UK, and there are already significant efforts in progress to develop detectors, using appropriate technologies,

which could begin operating in 2012.

Not only will the construc-tion and operation of such devices be educational in it-self, but they will be used for real physics research, and im-prove students STEM skills via hands on experiments. It is also planned that students will report their results and share best practice at an an-nual School Cosmic Ray De-tector Conference.

Funding for a national cos-mic ray detector network is expected to come partly from STFC, and other partners.

For more information about cosmic ray detector projects, please contact Neville Hollingworth at STFC ([email protected]).

By Neville Hollingworth (STFC) & Bruce Kennedy

(RAL/STFC)

IOP Half Day Report


mailto:[email protected]




There have been nine half-day meetings and we will have another two half-day meetings in 2011 bringing the total to eleven this year.

On the 12th January we had a Challenging the Standard Model at the High Energy Frontier meeting at Liver-pool. This meeting covered an introduction to our current theoretical knowledge of SM cross sections, in particular for jets, W and Z bosons and top pairs; experimental over-views and recent results from CMS, ATLAS and LHCb ex-periments; the interplay of SM measurements and searches; phenomenological and Monte Carlo tools.

On February 9th a meeting on the subject of Masterclasses was held at Birmingham, or-ganised by prof. Peter Watkins. On 23rd February at Oxford a half day workshop on Vector Boson Fusion was held, re-

viewing the theoretical calcu-lations, experimental analy-ses at the Tevatron and LHC and a review of the simula-tion status. Speakers in-cluded: Dieter Zeppenfeld, Markus Schumacher, Andy Pilkington

A Neutrino Physics meeting was held at Queen Mary Uni-versity on 18th April. It was organized by Francesca Di Lodovico and 57 participants from 18 institute attended. There were seven presenta-tions (two female and five male speakers).

The total number of atten-dees was almost 60 people ranging from PhD students to full professors. There were representative from all the relevant groups, and also par-ticipants not only from neu-trino groups. All speakers ac-cepted warmly the invitation. The workshop concentrated on the latest news (several) from neutrino oscillations, so there was both participation



and interest from the public to understand the issues.

The Top Quark Physics meet-ing, also at Queen Mary was held on the 18th May, orga-nized by Lucio Cerrito. There were 32 participants from 13 institutes, seven pre-sentations (three female, four male speakers). The meeting attracted 32 participants from Universities across the UK plus a number of QMUL stu-dents that joined for the pre-sentations. The programme included theory reviews of QCD production of top pairs by Dr. Adrian Signer (IPPP Durham) and a keynote pre-sentation on strategies for BSM searches with top signa-tures by Professor Fabio Mal-toni (UC Louvain, Belgium). The experimental panorama was discussed by speakers representing the ATLAS, CMS and the Tevatron exper-iments for a total of seven talks. Particularly stimulating discussions saw theorists de-bating the often controversial

definition of top quark mass and its relationship with the experimental measurements, and theorists and experimen-talists discussing on the pro-posals for new physics searches and the feasibility of new SM tests. Overall the meeting provided a forum for an enjoyable and informal gathering of UK-based phe-nomenologist and experi-mentalists working on top quark signatures (continued in the local pub afterwards), and enhanced the visibility of the UK community to one of the organizers of the bi-an-nual topical International Conference on Top Quark Physics, possibly strengthen-ing future international col-laborations.

On 1st July a Detectors for Particle Physics half day meeting was held at Royal Holloway. Organized by Norman McCubbin, there were 60 participants from 15 institutes and eight presenta-tions.



The IOP Dark Matter Meet-ing, was held at Kings Col-lege on 16th September, orga-nized by Fairbairn, Malcolm. There were eight presenta-tions.

On 12 October at UCL there was a Neutrinoless Double Beta Decay Meeting. give an overview of; the experi-mental status and future prospects of searches for neu-trinoless double beta decay; the status and progress in the determination of nuclear ma-trix elements; and the theoret-ical aspects and develop-ments of relevant models of lepton number violation.

There will be two further meetings this year, more in-formation can be found at http://www.heppcommunity.org.uk/?page_id=6

Dr. Melissa George and Dr. Cigdem Issever

Disclaimer: views ex-pressed herein are not nec-essarily those of the Insti-tute of Physics, nor are they indicative of any current or future policy of the Institute


http://www.heppcommunity.org.uk/?page_id=6

http://www.heppcommunity.org.uk/?page_id=6

newsletter issue 11 - institute of physics...iop hepp group newsletter: issue 11 november 2011...

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