Production of Eta-Mesons in 200 AGeV/c S+S and S+Au Reactions

Abstract

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

Postscript file, 14 pages, figures included, compressed and format, Accepted for publication in Phys. Lett. B