Collider workshop The promise of initial results after the tures. The distributions of charged experiments will shed more light on start of operations at CERN's SPS particles follow KNO (Koba/Niel- this question. proton-antiproton collider and the sen/Olesen) scaling, even at relative­ Cosmic ray experiments have ev­ prospects for high energy hadron ly high multiplicities. In contrast to ents in and beyond the energy range collisions at Fermilab (Tevatron) and the ISR data, some evidence for long attainable in the colliders. However Brookhaven (ISABELLE) provided a range correlations is seen. The aver­ this was the first time that laboratory timely impetus for the recent Topi­ age transverse momentum per parti­ and cosmic ray data could be expli­ cal Workshop on Forward Collider cle increases to 500 MeV. citly compared. Two cosmic ray Physics', held at Madison, Wiscon­ The UA1 experiment was able to findings are now confirmed — the sin, from 10—12 December. It be­ report relatively copious production rapidity plateau now extends to ±4, came the second such workshop to of events with high transverse ener­ and average transverse momentum be held, the first having been in 1979 gy. Previous experiments, notably per particle rises to 500 MeV. Pecu­ at the College de France, Paris. the NA5 study at the CERN SPS (see liar events, such as the much-publi­ The 100 or so participants had the May 1981 issue, page 155), found cized Centauro, have not yet been chance to hear preliminary results that such processes are relatively seen at collider experiments, but from the UA1, UA4 and UA5 exper­ abundant. Klaus Pretzl reviewed the could arise as a result of large high iments at the CERN SPS collider (see N A5 study with a calorimeter trigger. multiplicity fluctuations. January/February issue, page 3), to­ Events have been seen with trans­ New cosmic ray data from the gether with other new data, including verse energy of up to 18 GeV out of 'Fly's Eye' detector now operational that from proton-antiproton runs at 22 GeV available in the centre-of- in Utah were presented by G. Cassi- the CERN Intersecting Storage mass, over a rapidity range of ±0.8. day. This uses an arrangement of Rings. Jet production is certainly not evi­ mirrors and photomultipliers to ob­ As clear from the title of the Work­ dent. serve the radiation produced by ex­ shop, interest centred on interesting A related question is the effect of tensive air showers. It allows the physics from collisions whose pro­ fluctuations in the high multiplicity interaction point in the atmosphere ducts are confined in the 'forward' tail of the particle distributions. This to be located and thus determines angular region -— within 30° in the might be the reason why the events the absorption length of the proton- centre-of-mass. Nowadays, angle with large transverse energy appear nucleus collision. The aim is to meas­ has been replaced by rapidity as a to contain many particles with low ure total proton-nucleon reaction convenient variable, and this region energy. These fluctuations can pro­ rates down to millibarn levels at up to corresponds to ±5 rapidity units at duce peculiar neutral to charged pion 100 TeV in the centre-of-mass. Early the SPS and ±6 at the Tevatron, ratios and angular distributions. This results suggest that the total reac­ excluding a small central zone. might mean that particle jets are tion rate is still rising, even at these If they exist, long range correla­ there but are hard to find. energies. tions (similar phenomena seen under Related theoretical progress was Less spectacular but still important quite different kinematical con­ reported by Geoff Fox, who has been are the antiproton results emerging ditions) should be observable in this busy (with Robert Kelly) calculating from the CERN ISR. Data were pre­ angular range. Other expected pro­ QCD effects in hadron-hadron colli­ sented by P. Grannis, M. Block and cesses include production of weak sions, including gluon 'bremsstrah- L. Camilleri. bosons (the W and Z), heavy fla­ lung'. He finds that if the products of With hadron colliders promising vours), and maybe Higgs particles. high transverse momentum colli­ new discoveries, theorists were able However the copious production of sions are selected using a total trans­ to provide substantial input. One pions under these conditions makes verse energy trigger, rather than hav­ field ripe for further study is heavy for high backgrounds when trying to ing a planar jet structure, they are flavour production. Stan Brodsky pick out electrons and muons, and instead isotropic, with many gluons presented ideas of intrinsic flavours sophisticated detection techniques being radiated. This may be an expla­ in the nucleon which result in heavy are needed. nation for the non-appearance of jets flavour production at large energy The UA1 and UA5 results were under NA5 conditions. It could mean transfers. This could explain the rela­ presented by A. Kernan and that clean separation of jets from tively high charm production levels R. Meinke respectively. The data as background is difficult. Further data observed at the ISR, but production presented show three striking fea­ from the proton-antiproton collider of heavier flavours (beauty and top) 52 CERN Courier, March 1982 would provide an exacting test. on the high charm production levels the production of weak bosons, (These ideas have to be reconciled seen at the ISR, M. Jacob and R. Hor- Higgs particles, etc., were pre­ with recent data from Fermilab and gan have predicted that forward-pro­ sented. Hopefully at future such from the European Muon Collabora­ duced top particles should indeed meetings theorists will be able to fit tion's study of charm production by show up at high energy proton-anti- the observed data. high energy muon beams at the SPS.) proton colliders. At the Madison These meetings are now a regular While there is some evidence for meeting, R. Odorico presented other feature of the particle physics scene, beauty production at the ISR (pre­ arguments to explain the observed the next one being scheduled for sented at the meeting by D. Dibiton- charm production levels. Further stu­ 10-12 June in Rome. to), discovery of top flavour produc­ dies at colliders will certainly be use­ (We are grateful to D. Cline for pro­ tion at the SPS collider would help ful in solving this problem. viding us with the material from complete the picture. Also drawing At Madison, latest calculations on which this report was compiled.) Data (upper points) from the full wide-angle calorimeter of the NA5 experiment at CERN using a large transverse energy trigger. The relatively high reaction rates observed are difficult to reconcile with production of well-defined particle jets. Initial new calculations (by Geoffrey Fox and Robert Kelly) including gluon bremsstrahlung appear to provide a promising fit to the data at these transverse energies. CERN Courier, March 1982 53 .