R. Battiston

Observation of single isolated electrons of high transverse momentum in events with missing transverse energy at the CERN pp collider

Abstract We report the results of a search for single isolated electrons of high transverse momentum at the CERN p p collider. Above 15 GeV/c, four events are found having large missing transverse energy along a direction opposite in azimuth to that of the high-pT electron. Both the configuration of the events and their number are consistent with the expectations from the process p + p → W ± + anything , with W→e+ν, where W± is the charged Intermediate Vector Boso postulated by the unified electroweak theory.

Observation of Electrons Produced in Association with Hard Jets and Large Missing Transverse Momentum in p anti-p Collisions at s**(1/2) = 540-GeV

Abstract Using a sample of events collected by UA2 and corresponding to an integrated luminosity of 116 nb −1 . we have searched for electron-“neutrino” pairs in which the transverse momenta of the electron and of the “neutrino” exceed 15 GeV/c and 25 GeV/c respectively. A total of 35 events are observed in low background conditions. Most events can be interpreted in terms of W ± production from QCD processes. Events in which the observation of hard jets makes this interpretation unlikely are described in detail. Possible sources of background contamination are considered.

Measurement of Very Large Transverse Momentum Jet Production at the CERN anti-p p Collider

Abstract The production of very large transverse momentum hadron jets has been measured in the UA2 experiment at the CERN p p Collider for s = 540 GeV using a highly segmented calorimeter. The range of previously available cross sections for inclusive jet production is extended to pT = 150 GeV and the two-jet invariant mass distribution to mjj = 280 GeV with the largely increased data sample collected during the 1983 running period. The results are compared with the predictions of QCD models.

Search for decays of the W± and Z bosons into quark-antiquark pairs

Abstract The invariant mass distribution of jet pairs observed in the UA2 central calorimeter is examined in the search for an excess of events in the region of the W ± and Z bosons, which would reveal their decays into quark-antiquark pairs. We give a detailed account of the methods of analysis used to optimize the mass resolution achieving ≅±10%. A structure is observed at the level of ≅ 3 standard deviations in the mass region of W ± and Z with shape and position consistent with expectation from their qqdecays. It contains 632 ± 190 events, 1.4 standard deviations above the standard model prediction of 340 ± 80 events.