Systematics of inclusive photon production in 158·A GeV Pb induced reactions on Ni, Nb, and Pb targets

The multiplicity of inclusive photons has been measured on an event-by-event basis for 158·A GeV Pb induced reactions on Ni, Nb, and Pb targets. The systematics of the pseudorapidity densities at midrapidity (ρmax) and the width of the pseudorapidity distributions have been studied for varying centralities for these collisions. A power law fit to the photon yield as a function of the number of participating nucleons gives a value of 1.12±0.03 for the exponent. The mean transverse momentum, 〈pT〉, of photons determined from the ratio of the measured electromagnetic transverse energy and photon multiplicity, remains almost constant with increasing ρmax. Results are compared with model predictions.