Azimuthal anisotropy in S+Au reactions at 200 A GeV

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 employed 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. (C) 1997 Published by Elsevier Science B.V

Multiplicity and pseudorapidity distribution of photons in S+Au reaction at 200A GeV

The photon multiplicity has been measured for the first time in S+Au collisions at 200A GeV over a wide pseudorapidity range (2.8 less than or equal to eta less than or equal to 5.2) employing a fine granularity preshower detector. The pseudorapidity density of photons increases with centrality, reaching similar to 200 at the highest centrality studied. The results are compared with measurements of the charged particle multiplicity and with predictions of the VENUS event generator

Soft photon production in central 200 GeV nucleon S-32+Au collisions

Inclusive photons of low transverse momenta have been measured in 200 GeV/nucleon S-32+Au collisions at the CERN SPS. Data were taken in the WA93 experiment using a small acceptance BGO detector with longitudinal segmentation. The results are compared to WA80 measurements for the same system and results from hadron decay calculations, An excess of soft photons over the expectations from neutral meson decays is observed