A Circumstantial Evidence for the Possible Production of QGP in the 158A GeV/c Central Pb+Pb Collisions

Abstract：

Hadron and string cascade model (JPCIAE),based on the hypothesis without introducing the quark gluon plasma(QGP),is employed to study the direct photon and π 0 transverse momentum distributions for central ²⁰⁸Pb+²⁰⁸Pb collisions at 158A GeV/c. The theoretical results of transverse momentum distribution for both the direct photon and the π⁰ particle are lower than the data of WA98 experiment. However,JPCIAE model can ever explain successfully the results of WA80 and WA93 experiments of central S+Au collisions at 200A GeV/c where there is no evidence of direct photon excess. Having considered the results of WA80 and WA93 experiments can be explained but WA98's can't,that might provide a circumstantial evidence for the possible production of QGP in the high energy central Pb+Pb collisions.