Champagne at the CERN SPS. Research Director Erwin Gabathuler (second from left) had promised a crate of champagne if the maximum proton-antiproton collision luminosity achieved in the SPS during the initial operations in 1981 could be increased tenfold. Enjoying his generous offer with him are (left to right) Andre Faugier, Lyndon Evans, Jacques Gareyte and Robin Lauckner.
(Photo CERN 209.11.82)
The first sign that beauty meson reconstruction might be possible was the observation that various different charmed mesons were be ing produced (see December 1982 issue, page 418). With these charmed particles reconstructed, the next step was to try to work back to the original beauty mesons from the data around the fourth upsilon. The search concentrated on allowed combinations of charmed mesons plus one or two pions, rather than more frequent (but more compli cated) decays producing more parti cles. After careful selection, a clear peak of 18 events showed up in the mass region between 5265 and 5285 MeV, where the scale is ad justed to agree with the precision measurement of the upsilon mass in the VEPP-4 ring at Novosibirsk (see October 1982 issue, page 325). Background effects were carefully al lowed for in order to detect any me chanism which could fake the ob their first taste of physics at these the first time in the latest period. served peak. record energies in 1981, and inter Another major factor which made for This important observation at esting first results emerged from the higher luminosity (collisron rate) was CESR will be reported in more detail meagre samples of data which were that several circulating antiproton in the next issue. It is a significant collected. Now the experiments bunches became available for colli milestone in new particle spectros have been able to accumulate about sion with proton bunches moving in copy, and the hope is that increased five hundred times as much data as the opposite direction. In addition, data samples will soon open up this before, and the new physics results the Antiproton Accumulator Ring field for more detailed study. are eagerly waited. and the PS complex which together Proton-antiproton operation had supply the precious antiprotons been scheduled earlier last year, but were able to boost the supply of anti CERN a mishap at the UA1 experiment matter available. When antimatter meant that it had to be postponed. The period began modestly mattered This proved to be something of a enough early in October, when there blessing in disguise. Two periods of were teething troubles. After several On 6 December, the highly success collider operation were merged into days the linac ion source went out of ful 1982 period for proton-antipro- an almost continuous block, which action, which meant that the Anti ton collisions in the SPS ring came to made for considerable savings in proton Accumulator was left with a an end. For almost two months, the setting-up and running-in. In this way substantial stack of antiprotons, but big UA1 and UA2 experiments were the experiments were able to have there were no protons to collide able to log particle collisions at the the continuous supply of collisions them with. The decision was made highest man-made energies (540 which they need. to try for antiproton injection into the GeV) ever achieved, and at a sub The 'low beta' insertions to LEAR low energy antiproton ring. stantial rate. squeeze the beams together in the After some trepidation at such short The SPS collider experiments had collision areas came into action for notice, the resourceful PS operations
6 CERN Courier, January/February 1983 The second half of the latest period of proton-antiproton collisions in the CERN * Preliminary proton-anti SPS. For each injection, initial luminosity regularly surpassed 1028 cm~2 s~1. Total proton data was reported integrated luminosity over the whole period at January's Topical (which began in October) was more than 25 inverse nanobarns, good news for the Workshop on Collider big experiments. Physics, held in Rome. Fixed Target Workshop PP LUMINOSITY With the first generation of fixed tar get experiments at the 400 GeV SPS proton synchrotron completed or nearing completion, with SPS pro ton-antiproton collider operation well established, with LEP construc tion imminent, and with the closure of the Intersecting Storage Rings planned, it is a propitious time to review the programme of fixed tar get experiments at the SPS and to look ahead. So at the end of last year CERN decided to sponsor a comprehensive workshop, which was organized by I. Mannelli, to review the physics which could be covered with the ma chine during the second half of the current decade. This physics poten tial has to take particular account of the different conditions which can be studied at the SPS proton-antiproton collider, and of the start of opera team successfully decelerated the UA4 experiment could take valuable tions at the Fermilab Tevatron. 3.5 GeV/c antiprotons from the AA data on elastic scattering. The field was divided into five main down to 600 MeV/c, and the beam Then there were a few hitches, but areas — neutrino physics (convener circulated happily in the 80 m peri everything came back with a bang at D. Haidt), muon physics and struc meter LEAR ring. the middle of November with a new ture functions (J.-J. Aubert), new With the proton supply reestab luminosity record of over 3 x 1028, particles (L. Foa), hadron physics lished, the proton-antiproton lumi and champagne was called for. To (D. Treille) and nuclear beams and nosity gradually built up, briefly wards the end of the period, this level targets (W. Willis). Working groups reaching a new record level of 1028 was surpassed several times. The were set up and met periodically dur cm-2 s-1 on 12 October. In mid- final record luminosity was 5 x 1028. ing the autumn, but the workshop October, first trials began with three Typical beam coasting time was 15- was concentrated mainly into a week bunches each of circulating protons 20 hours, although one antiproton of parallel and plenary sessions at and antiprotons. This proved tricky shot lasted for 42 hours. CERN at the beginning of Decem to master, but by the end of October, At the end of the run, the total ber. three bunches on three became the number of interactions — the inte The plenary sessions presented a standard pattern, injection luminosi grated luminosity — exceeded 25 condensed version of what had been ties around the 1028 level were the inverse nanobarns, most of which discussed earlier in the various work norm, and the experimenters ac was recorded by the experiments. ing groups and parallel sessions, but knowledged that they were confi According to the theory, this should this compression of material contin dently logging lots of data with low be sufficient for the production of ued on the final day of the workshop, backgrounds. some intermediate bosons of the when the five conveners summar At the beginning of November, charged kind. While waiting for the ized what had been discussed under there was a brief pause before the next run in April, there are many each heading. period was continued, initially in bright eyes scouring the data* As well as paving the way for 'high beta' configuration so that the specific future studies at the SPS, it
CERN Courier, January/February 1983 7