Centrality dependence of K+ produced in Pb+Pb collisions at 158 GeV per   nucleon
  The NA52 collaboration searches 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 hadron to quark-gluon plasma (QGP) phase transition. The K+ yield is found to grow proportional 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 e.g. p+A data at the same \sqrt{s}- in a chemically equilibrated phase. 
NA52 collaboration: R. Arsenescu, C. Baglin, H. P. Beck, K. Borer, A.   Bussiere, K. Elsener, Ph. Gorodetzky, J. P. Guillaud...