Elliptic emission of K+ and pi(+) in 158 A center dot GeV Pb + Pb collisions

An event-by-event analysis of the azimuthal angular correlation with respect to the reaction plane has been carried out for K+ and pi(+) emission near mid-rapidity in 158 A . GeV Pb + Pb collisions. In semi-central collisions, K+ mesons are found to be preferentially emitted out of the reaction plane, while pi(+) mesons are emitted in the reaction plane. The results suggest that the kaon emission is influenced by in-medium potential effects in addition to collective flow effects. (C) 1999 Published by Elsevier Science B.V. All rights reserved

Delta(++) production in 158 A GeV Pb-208+Pb-208 interactions at the CERN SPS

The Delta(++)-resonance production in central 158 A GeV Pb-208 + Pb-208 collisions at the CERN SPS has been studied. The Delta(++) production was estimated from the invariant mass spectrum of p pi(+)-pairs by subtracting a mixed event background. The measured Delta(++) abundance is compared with the results from other experiments at lower energies, and with a model calculation assuming thermal and chemical equilibrium. (C) 2000 Elsevier Science B.V. All rights reserved

Scaling of particle and transverse energy production in 208Pb+208Pb collisions at 158·A GeV

Transverse energy, charged particle pseudorapidity distributions and photon transverse momentum spectra have been studied as a function of the number of participants (N-part) and the number of binary nucleon-nucleon collisions (N-coll) in 158.A GeV Pb+Pb collisions over a wide impact parameter range. A scaling of the transverse energy pseudorapidity density at midrapidity as similar to N-part(1.08+/-0.06) and similar toN(coll)(0.83+/-0.05) is part coil observed. For the charged particle pseudorapidity density at midrapidity we find a scaling as similar to N-part(1.07+/-0.04) and similar toN(coll)(0.82+/-0.03). This faster than linear scaling with N-part indicates a violation of the naive Wounded Nucleon Model

First evidence of directed flow at 158 A GeV Pb+Pb collisions in WA98 experiment

The first evidence of directed flow at 158 A GeV Pb + Pb collisions is observed using the Plastic Ball detector in WA98 experiment. The azimuthal angle of the total transverse energy, Phi(o), is determined for each event using the observed protons in the Plastic Ball. A clear azimuthal asymmetry of fragments is observed with respect to Phi(o). The degree of azimuthal asymmetry is found to be largest in mid-central collisions, which is consistent with the picture of the collective flow. The p(t) spectra of particles measured in the mid-rapidity spectrometer has been studied in conjunction with the Plastic Ball, and different p(t) slopes with respect to Phi(o) for proton and pi(+) are observed

Elizabeth Buck, flute

Lukas FossPaul SchoenfieldLowell LiebermannChristopher RouseJoan TowerHenryk Mikolaj GoreckiTobias PickerMichael TorkeArnold Blac

Localized charged-neutral fluctuations in 158A GeVPb plus Pb collisions

Localized fluctuations in the multiplicity of charged particles and photons produced in central 158A GeV/c Pb+Pb collisions are studied. The charged versus neutral correlations in common eta-phi phase space regions of varying azimuthal size are analyzed by two different methods. The analysis provides a model-independent demonstration of nonstatistical fluctuations in both charged particle and photon multiplicities in limited azimuthal regions. However, no correlated charge-neutral fluctuations are observed, contrary to expectations for the production of a disoriented chiral condensate. The result is not explained by the widely used VENUS model