Production of η mesons in 200 AGeV/cS+S and S+Au reactions

Abstract Minimum Bias production cross sections of η mesons have been measured in 200 A GeV/ c S+Au and S+S collisions at the CERN SPS by reconstructing the η → γγ decay. The measurements have been made over the rapidity range 2.1 ≤ y ≤ 2.9 using the leadglass spectrometer of WA80. Within the statistical and systematical uncertainties the spectral shapes of π 0 and η mesons yields are identical when their invariant differential cross section is plotted as a function of the transverse mass. The relative normalization of the η to π 0 transverse mass spectra is found to be 0.53±0.07 for S+Au and 0.43±0.15 for S+S reactions. Extrapolation to full phase space leads to an integrated cross section ratio of η to π 0 mesons of 0.147±0.017(stat.)±0.015(syst.), and 0.120±0.034(stat.)±0.022(syst.) for S+Au and S+S collisions, respectively.