J.M. Rubio

Azimuthal anisotropy in S + Au reactions at 200 A GeV

Abstract Azimuthal correlations of photons produced at mid-rapidity in 200 A GeV S + Au collisions have been studied using a preshower photon multiplicity detector in the WA93 experiment. The Fourier expansion method has been employd to estimate the event plane via the anisotropy of the event as a function of centrality. The event plane correlation technique has been used to determine the true event anisotropy, beyond the anisotropy which arises due to finite multiplicity. The VENUS event generator with rescattering and proper simulation of the detector response can explain only a portion of the observed anisotropy. The residual anisotropy is found to be of the order of 5% for semi-central collisions. This suggests that directed collective flow of the produced particles is present at SPS energies.

Performance of a light emitting multistep avalanche chamber tracking system in Pb+Pb collisions

Abstract The construction and operation of light emitting multistep avalanche chambers will be described. Based on a preliminary analysis of data taken during the first Pb ion run at CERN the performance and operation of the tracking system will be discussed.

Event by event measurement of 〈pT〉 of photons in S + Au collisions at 200 A·GeV

The mean transverse momentum of photons has been determined on an event by event basis in S + Au collisions at 200 A.GeV from the ratio of the measured electromagnetic transverse energy (E-T(em)) to the photon multiplicity (N-gamma). The average value obtained is similar to that determined for the same system using spectroscopic techniques. The centrality dependence of the measured values are in agreement with the predictions of the VENUS event generator

A large-acceptance spectrometer for tracking in a high-multiplicity environment, based on space point measurements and high-resolution time-of-flight

A large acceptance tracking system, specially developed for tracking at very high particle densities encountered in ultra-relativistic heavy-ion collisions is described. The system is a combination of multi-step avalanche chambers equipped with electronic pad readout with high position resolution in two dimensions and streamer-tube detectors with pad readout, with coarser position resolution, that is sufficient for safe pattern recognition. A high-resolution time-of-flight system (time resolution better than 90 ps) provides particle identification up to 8 GeV/c for pions and protons and pion/kaon separation up to 4 GeV/c. All detectors in the tracking system are read out with new, high-performance integrated circuits. The system can operate at high event rates due to efficient zero suppression. The performance of the system for tracking under real running conditions with Pb-beam at 158 A GeV in the WA98 experiment at CERN is presented

MOMENTUM DISTRIBUTIONS AND INTERFEROMETRY ANALYSIS OF NEGATIVELY CHARGED HADRONS FROM 200 A GEV S+AU REACTIONS

Abstract Two particle correlations and single particle P T distributions have been measured for negatively charged hadrons from 200 A GeV S+Au reactions. The large acceptance of the WA93 dipole spectrometer enables the study of transverse momentum dependence of the multi-dimensional correlation function. A longitudinal radius decreasing with increasing transverse momentum is observed.