L. Rasmussen

MEASUREMENT OF THE STANDARD MODEL PARAMETERS FROM A STUDY OF W AND Z BOSONS

Abstract A study has been made of the decays W → ev and Z → e + e − , using the UA2 detector at the CERN pp Collider. The data correspond to an integrated luminosity of 142 nb −1 at a centre-of-mass collision energy √ s =546 GeV, and 768 nb −1 at √ s =630 GeV. Measurements of the standard model parameters from samples of 251 W decay and 39 Z decay candidates are compared with expectations of the standard electroweak model.

Measurement of the s**(1/2) Dependence of Jet Production at the CERN anti-p p Collider

Abstract The production of very large transverse momentum ( p T ) hadron jets has been measured in the UA2 experiment at the CERN p p Collider for s =630 GeV . The inclusive jet production cross sections exhibit a p T -dependent increase with respect to the s =546 GeV data from previous Collider runs. This increase can be described both by QCD calculations and by approximate x T =2 p T /√ s scaling. No significant deviation of the data from QCD predictions is observed at very large p T , placing a lower limit on the characteristic scale Λ c of a hypothetical superstrong contact interaction responsible for the binding of preons in the quark ( Λ c >370 GeV at 95% CL).

Search for exotic processes at the CERN pp̄ collider

Abstract The total UA2 data sample at the CERN pp Collider corresponds to an integrated luminosity of 910 nb −1 . Limits on various hypothetical processes, such as production of excited electrons, additional charged or neutral vector bosons, or supersymmetric particles, are presented from the analysis of this sample.

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.

MEASUREMENT OF THE STRONG COUPLING CONSTANT ALPHA-s FROM A STUDY OF W BOSONS PRODUCED IN ASSOCIATION WITH JETS

Abstract The UA2 experiment at the CERN p p Collider has identified a total sample of 251 W→eν events. Among this sample 221 events are found without jets and 29 with one jet. The yield of one-jet events relative to that of zero-jet events provides a measurement of the strong coupling constant: αs(Mw2)=0.13±0.03(stat)±0.03±(syst1)±0.02(syst2), where syst1 represents the experimental systematic error and syst2 is an estimate of the theoretical uncertainty.

Direct photon production in\(\bar pp\) in collisions at\(\sqrt s = 630\) GeV

AbstractA measurement of the direct production of photons with high transverse momentum from

Jet Measures and Hadronic Event Shapes at the {CERN}

\bar pp

Collider

collisions at