Secondary collision and the enhancement of the K+/π+ ratio in the high energy heavy-ion collision

The enhancement of K+/π+ ratio in the high energy heavy-ion collision is believed to be a possible signature of the formation of the quark gluon plasma. Based on the Participant Nucleon Model and the concept of the formation time of secondary particles, the K+/π+ ratio in the central collision of Si(14.5 GeV/c) and Au are calculated by Monte Carlo simulation. The following secondary collisions are considered, πN → K+Y, ππ → KK-bar and the single charge exchange reaction between pions and nucleons. The calculation results show that the increased K+/π+ ratio caused by these secondary collisions is not enough to explain the experimental data observed by the E802 group at BNL