Uppsala spells hope

Abdus Salam (front row, right) leads the notetakers at a plenary session of the recent EPS International High Energy Physics Conference, held in Uppsala, Sweden.

In the last few years, the particle physics community has experi­ enced something of a backlash. Indications of effects beyond its Standard Model - the electroweak synthesis plus the quantum chro- modynamics (QCD) picture of quark interactions - have disappeared on closer scrutiny, while the ex­ pected sixth ('top') quark is still missing. In addition, the proton does not appear to decay, at least not within 1032 years, ruling out the simplest 'grand unified' models encompassing both the electro- weak and the quark interaction sectors. However at the European Physi­ cal Society's International High Energy Physics Conference in Upp­ sala, Sweden, from 25 June to 1 July, the message was one of hope. There are excellent pros­ pects of unravelling good physics the monopoly of the UA1 and UA2 reviewed the present status of this with the impressive range of accel­ experiments at the CERN proton- research. It is not yet clear whether erators and storage rings planned antiproton collider for W and Z these materials will be suitable for or under construction. This tran­ physics with the first W and Z making superconducting magnets. sition to a new energy range was candidate events from the CDF Dave Jackson, reviewing the status reflected in the plenary talks, in­ detector at the Fermilab Tevatron. of the US SSC Superconducting cluding many status reports on Although presented as candidates, Supercollider project, did not con­ new projects. plenary speaker Pierre Darriulat of sider them significant at the pre­ The 600 physicists who came CERN and the UA2 experiment sent stage of the SSC design. to Sweden's oldest university, was convinced enough to invite In his talk on particle physics founded 510 years ago, heard the the CDF team to join the W/Z club. and cosmology, John Ellis of CERN first results from the new Japanese With CERN's new ACOL Anti- presented the emerging view on TRISTAN electron-positron collider. proton Collector coming into oper­ the supernova physics. He also With the machine running at 25 ation to boost the antiproton sup­ stressed the importance of the GeV per beam, the VENUS, AMY ply, exciting competition is fore­ 'dark matter' problem - gravita­ and TOPAZ experiments compare seen between Europe and the US. tional indications that much of the the production levels of hadrons In his summary, Guido Altarelli material of the universe is electro- and of muons. Their results so far pointed out that two of the big magnetically invisible. Many pro­ are compatible with what was seen physics discoveries of the past posed solutions imply the exist­ at slightly lower energies in the year were in other fields but never­ ence of new particles, and inge­ PETRA ring at the German DESY theless have important implications nious new detectors are being Laboratory several years ago and for high energy physics - the dis­ designed. as yet show no signs of the top covery of the new high tempera­ Terence Sloan reviewed quark quark. ture superconductors and the ob­ interactions deep inside hadrons, Key ingredients in the Standard servation of the 1987 supernova. and the measured structure func­ Model are of course the W and Z One of the pioneers of the new tions describing the quark content bosons carrying the weak nuclear boom in ceramic superconductors of nucléons and other particles. force. Uppsala marked the end of - Georg Bednorz of IBM Zurich - Recent results from the European

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CERN Courier, September 1987 3 experiments also took data with protons, an effort is being made to sort out collective effects. With new precision data on deep inelastic scattering probing the Beauty without charm deep interior of the struck nu­ cléons, the ratio of the longitudinal to transverse production rates New physics result announced Together with recent results measured at Stanford in certain at the International Symposium from the same experiment on kinematic regions (momentum on Lepton and Photon Inter­ the 'mixing' of electrically neutral transfer less than 10 GeV2) is larg­ actions at High Energy held in B mesons, this information helps er than the theoretical predictions. Hamburg from 27-31 July was fill in the gaps in the (Kobayashi- Elsewhere this ratio and the proton the evidence from the ARGUS Maskawa) matrix describing the structure function behave as ex­ experiment at the DORIS elec­ transitions between the different pected. tron-positron collider of the Ger­ types of quark, and hinting at man DES Y Laboratory (also in where the long-awaited sixth The session on the weak decays Hamburg) for the decay of B ('top') quark might be found. of quarks included the now famous mesons (carrying the beauty In his review talk at the Ham­ result from the ARGUS experiment quantum number) without pro­ burg meeting, W. Schmidt- at DESY on particle mixing in the ducing particles carrying the Parzefall of the ARGUS group neutral B meson system. The high charm quantum number. gave the majority view of a top level of mixing seen places a res­ triction on the top quark mass. The highly unstable B mesons quark heavier than 50 GeV. The With three families of two quarks, prefer to decay into charmed meson composed of this quark the top quark has to be heavier particles (also unstable) but less and its antiquark should thus than about 45 GeV. frequently they should decay be heavier than about 100 GeV, directly into particles carrying with implications for electron- The great message from the everyday ('up' and 'down') positron colliders starting oper­ conference was the possibility of quarks. ARGUS looked for B ations (TRISTAN, Japan), about a second Copernican revolution. decays into two-body states to start operations (SLC, Stan­ We are not at the centre of the disintegrating in turn into a pro­ ford), and soon to start opera­ universe and not even made of the ton and an antiproton together tions (LEP, CERN). most abundant form of matter in it. with one or two pions, and A full report on the Hamburg While there were no spectacular found them at the level of a few meeting will appear in our Octo­ new discoveries presented at this in ten thousand. ber issue. Conference, there was an impres­ sive amount of solid experimental and theoretical work reported. Promising developments in exper­ imental techniques were discussed twice, rather than once. A newcomer topic was high such as high power acceleration Despite reports earlier this year energy nuclear collisions. Five devices - the free electron laser on the observation of neutrinoless groups presented their results from (1.8 GW, 8.6 mm), the relativistic double beta decay accompanied data taken at CERN only seven klystron and the wake-field trans­ by the emission of new particles months earlier. The great hope is former (8 MeV/m). In the session (majorons), the results presented to see the long-awaited quark- on detector developments it was at Uppsala gave no support. Like­ gluon plasma, when quarks break shown that energy in the TeV wise a hint of special 'second-class loose from their habitual nucléon range can be measured with a pre­ currents' in certain tau decays re­ environments. The dimuon signals cision of one per cent using calo- ported by the HRS group at the reported by the NA38 collaboration rimetric methods and that two- Stanford linac (see April issue, hint at the suppression of the pro­ dimensional position measure­ page 10) was ruled out by several duction of J/psi particles, as pre­ ments in the micron range can be groups. dicted for the plasma. Since all made, promising for the future.

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6 CERN Courier, September 1987 The atmosphere in Uppsala was full of enthusiasm when we now enter the era of post-W/Z physics. Maybe some of the hopes will have materialized by the time of the 1989 EPS conference in Madrid.

Reported by Lars Bergstrôm and Sven Kullander.

Reinhold Ruckl (left) and Roberto Peccei at the HEP 87 club.

(Photos UNT Bild Uppsala)

Pushing hard on the accelerator

The quest for new techniques to Smith reviewed the physics moti­ After all the thought, discussion drive future generations of particle vations for higher energies, under­ and experimental work of recent accelerators has been pushed hard lining the rich rewards expected years, a certain confidence and in recent years, efforts having been when constituent particles collide consensus viewpoint is now highlighted by workshops in Eu­ at energies around 1 TeV (1000 emerging. The so-called 'semi- rope, organized by the European GeV). Major areas of new acceler­ conventional linac' is a clear favou­ Committee for Future Accelerators, ator activity were described by rite for the next generation of elec­ and in the US. H. Henke, S. Aronson, J.-L. Bobin, tron-positron colliders, while the The latest ECFA Workshop on R. Palmer, J. Seeman and J. Shep- more exotic techniques using plas­ New Developments in Particle Ac­ pard, while Carlo Rubbia looked mas, laser switching, wake fields, celeration Techniques, held at at the choices ahead (see page crystals, etc., have not yet pro­ Orsay from 29 June to 4 July, 11). duced a definitive candidate, and showed how the initial frantic After this general survey, the are thought to be relevant to a search for innovation is now ma­ mornings were given over to sym­ subsequent generation of ma­ turing. posium-style talks on new devel­ chines. After Michel Davier, Head of the opments, with the afternoons re­ The semi-conventional linac work host Laboratoire de l'Accélérateur served for working groups in paral­ centres on the CLIC (CERN Linear Linéaire at Orsay, opened the lel sessions. The final day saw Collider) and SC (Stanford Collider) meeting by recalling some import­ summaries from these working schemes. These are both based ant milestones in accelerator his­ groups, together with a round- on classical room temperature tory, business began with a series table discussion chaired by Kjell copper accelerating structures of invited talks. Chris Llewellyn- Johnsen. operating at high frequencies to

CERN Courier, September 1987 7