V. Cavasinni

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.

A modular drift-chamber vertex detector at the CERN ISR

Abstract The vertex detector built by the Pisa Group for the CERN Intersecting Storage Rings muon pair experiment R 209 is described. A modular system of 136 small drift chambers, assembled around the ISR intersection region, measures the entrance directions of the muon pairs into the magnetized iron spectrometer, and the directions of the charged hadrons produced in association. Each module contains two doublets of sense wires, each doublet being associated with one delay line to determine directly the space points without left-right ambiguities. The mechanical structure is rather unconventional, having been designed with the aim of minimizing any dead space in the assembly of the modules. Space resolution is ≈ ± 0.2 mm in the drift coordinate and ≈ ± 2mm in the delay coordinate.

Contribution of hard QCD interactions to the pp̄-pp total inelastic cross-section difference at the CERN ISR energies

Abstract We have performed a first-order QCD calculation to evaluate a possible contribution of large-Q02 scattering to the pp/pp total inelastic cross-section difference at the CERN intersecting storage rings (ISR). We found that at s =31 GeV and for Q2≳6 GeV2 there is a small (a few microbarns, but definitely not 0) difference in favour of the pp reaction. This effect is confined to the central rapidity region (|y|≲1) and diminishes with increasing centre-of-mass energy.