Centrality dependence of K+ produced in Pb + Pb collisions at 158 GeV/nucleon

The NA52 collaboration is searching for a discontinuous behaviour of charged kaons produced in Pb + Pb collisions at 158 A GeV as a function of the impact parameter, which could reveal a quark-gluon plasma phase transition. The K+ yield is found to grow proportionally to the number of participating (`wounded') nucleons N, above N = 100. Previous NA52 data agree with the above finding and show a discontinuous behaviour in the kaon centrality dependence near N = 100, marking the onset of strangeness enhancement, over, for example, p + A data at the same (s)1/2, in a chemically equilibrated phase.