The Z as seen by the CDF detector at the Fermilab Tevatron.

FERMILAB One year Tevatron run

The Fermilab 1988-89 900 GeV on 900 GeV proton-antiproton collider run was successfully ended on 1 June, having started on 20 June last year! During this period the ac- celerator supplied a world record of 9590 inverse nanobarns of colli• sions to the CDF detector. Beam was stored for over 4257 hours, and peak luminosity was about 2.06 x 1030. The best integrated luminosity in one week was 518 inverse nanobarns. During the run there were 925 stores, of which 133 were ended intentionally, the average length of those stores end- ing by failure being 9.48 hours. Last June, the goal had been to collect 1 inverse picobarn (1036 cm"2) of integrated luminosity on tape. Reality tumed out even better than expectations, and about 4.7 units had been collected by the for offline analysis - a total of 0.3 ± 0.2 GeV, consistent with time the run ended. about 5500 9-track tapes, contain- the earlier measurements by the A friendly compétition between ing about 6 million events. Offline UA1 and UA2 experiments at shift crews to see who could write event reconstruction on a large CERN's proton-antiproton collider, the most data to tape in a single scale began on two 65-node ACP but with improved magnetic analy• eight-hour shift resulted in a record Systems operated by the Fermilab sis. of 26 inverse nanobarns, almost as Computing Department at the start The continuing data analysis will much as was collected during the of the year. keep the CDF group busy until the entire 1987 run. The record for a However to get an early look at next Collider run begins in 1991. single week was about 0.3 inverse interesting physics, certain event picobarn to tape. types were selected for full recon• To cope with this high perfor• struction in a spécial production cy• mance, the experiment used a trig- cle. Based on a preliminary event ger System with four levels. Levels sélection, about 600 Z decays into CERN 0, 1 and 2 were debugged last électron-positron pairs and about summer and were fully operational 5000 W decays into an électron Record antiproton by September. The event rejection and a neutrino were identified, and performances power of the Level 3 trigger Sys• the search for the elusive sixth tem, consisting of about 50 Ad• 'top' quark was begun. vanced Computer Program (ACP) The first resuit to émerge is the CERN's 1988-9 antiproton opéra• nodes, was steadily increased dur• mass of the Z. Using the entire 4.7 tions were separated by a three- ing the run, eventually attaining a inverse picobarn data sample, the month shutdown at the beginning factor of about 3. CDF resuit, based on 64 Z decays of this year. In two three-month Events passing the Level 3 trig• into électron-positron pairs and runs, the SPS supplied 7810 in• ger were written to magnetic tape 132 into muon pairs, is 90.9 ± verse nanobarns of proton-antipro-

CERN Courier, September 1989 13 Around the Laboratories

* See page 37 ton collisions (3372 of which were While the Z has become the bu• in the 1988 run) over a total stored siness of the LEP and SLC électron- SUPERCOLLIDER beam time of 2450 hours (1206 in positron colliders, thèse machines Update* 1988). do not yet have enough collision (The performance of a colliding energy to form the electrically- beam machine is measured by its charged Ws, which would have to With final fédéral funding décisions luminosity' - the number of parti• be produced in pairs. Thus W in• still in the pipeline, the US Depart• cles per second in one beam times formation from the experiments at ment of Energy's January confirma• the number of particles per unit the proton-antiproton colliders will tion of the Ellis County, Texas, site area intercepted in the other beam. continue to provide important phy• for the proposed US Superconduct• In particle collisions, areas are sics input. ing Supercollider (SSC) was accom- measured in terms of 'barn' units panied by a promise of some of 10~24 sq cm, the term deriving $1,000 million of Texas state con• from a physics remark by Niels struction money. The 84 kilomètre Bohr - 'as easy as hitting a barn'. ring to collide 20 TeV (20,000 For particle collisions, a barn is gi- GeV) proton beams would be built gantic - millibarns and nanobarns underground about 40 km south of are the norm. Accumulated colli• Dallas, within easy reach of Dallas- sion data is metered by 'integrated Fort Worth airport, in a semirural luminosity', expressed as inverse setting of flat and gently rolling nanobarns or inverse picobarns - a prairies. thousand of the former being équi• Construction and opération of valent to one of the latter.) the SSC would be managed for the Peak SPS collider luminosity oc- Department of Energy by the Uni• curred on 25 May with 2.95 x 1030 versités Research Association per sq cm per s. The best resuit (URA), the consortium of 72 uni• from a single store was the 97 in• versités which currently opérâtes verse nanobarns on 7 June, but 14 Fermilab. For the SSC venture, May had seen 120 inverse nano• URA has two industrial partners - barns in a single day. The longest EG and G Inc, which provides engi• SPS store lasted for 45.5 hours. neering, logistic and other technical Upstream, the antiproton supply support, and the Sverdrup Corp., attained new highs. The endurance with extensive expérience in the record for a stack in the AA anti• management of large construction proton accumulator was almost 48 projects. days. A best of more than 1012 Roy F. Schwitters of Harvard, particles came on 8 June, and a co-spokesman of the Collider De• peak hourly stacking rate of 5.8 x tector at Fermilab (CDF) group, and 1010 on 28 May. Thèse perfor• a member of the team which dis- mances underlined the success of covered the hidden charm of the the ACOL project in upgrading J/psi particle at Stanford's SPEAR CERN's antiproton capacity. électron-positron ring in the mid- Physics dividends will émerge in 70s, has been named Laboratory the coming months. One resuit was Director. the new record low antiproton én• Appointed Deputy Laboratory Di• ergies (see page 23). rector and Construction Project At the International Lepton/Pho- Manager is Richard Briggs, formerly ton Symposium held at Stanford in Associate Director for the beam re- August, the UA2 collaboration search and magnetic fusion energy gave new results for the masses of programmes at Livermore. The both the Z and W particles. Magnet Division will be led by Tho-

14 CERN Courier, September 1989