Ξ and Ξ production in 158 GeV/nucleon Pb + Pb collisions

Abstract We report measurements of Ξ − and Ξ + hyperon absolute yields as a function of rapidity in 158 GeV/c Pb+Pb collisions. At midrapidity, dN / dy =2.29±0.12 for Ξ − , and 0.52±0.05 for Ξ + , leading to the ratio of Ξ + /Ξ − =0.23±0.03 . Inverse slope parameters fitted to the measured transverse mass spectra are of the order of T ≈300 MeV near mid-rapidity. The estimated total yield of Ξ − particles in Pb+Pb central interactions amounts to 7.4±1.0 per collision. Comparison to Ξ − production in properly scaled p+p reactions at the same energy reveals a dramatic enhancement (about one order of magnitude) of Ξ − production in Pb+Pb central collisions over elementary hadron interactions.