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

Centrality dependence of charged-neutral particle fluctuations in 158A (GeVPb)-Pb-208+Pb-208 collisions

Results on the study of localized fluctuations in the multiplicity of charged particles and photons produced in 158A GeV/c Pb+Pb collisions are presented for varying centralities. The charged versus neutral particle multiplicity correlations in common phase space regions of varying azimuthal sizes are analyzed by two different methods. Various types of mixed events are constructed to probe fluctuations arising from different sources. The measured results are compared to those from simulations and from mixed events. The comparison indicates the presence of nonstatistical fluctuations in both the charged particle and photon multiplicities in limited azimuthal regions. However, no correlated charged-neutral fluctuations, a possible signature of formation of disoriented chiral condensates, are observed. An upper limit on the production of disoriented chiral condensates is set

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

Centrality and transverse momentum dependence of collective flow in 158 A GeV Pb+Pb collisions measured via inclusive photons

Directed and elliptic flow of inclusive photons near mid-rapidity in 158 A GeV Pb + Pb collisions has been studied. The data have been obtained with the photon spectrometer LEDA of the WA98 experiment at the CERN SPS. The flow strength has been measured for various centralities as a function of p(T) and rapidity over 0. 18 <p(T) <1.5 GeV/c and 2.3 <y <2.9. The angular anisotropy has been studied relative to an event plane obtained in the target fragmentation region that shows the elliptic flow to be in-plane. The elliptic flow has also been studied using two-particle correlations and shown to give similar results. A small directed flow component is observed. Both the directed and elliptic flow strengths increase with p(T). The photon flow results are used to estimate the corresponding neutral pion flow. (c) 2005 Elsevier B.V. All rights reserved

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