J/psi normal and anomalous suppressions in a hadron and string cascade model

A mechanism for the effective dissociation of a c (c) over bar pair in the colour electric field of strings is introduced into a hadron and string cas cade model, i.e. JPCIAE, which is based on the LUND model, simulating ultra -relativistic nucleus-nucleus collisions. This new mechanism together with the known mechanism of nuclear absorption (both baryons and mesons) could r eproduce fairly the data of the normal and anomalous J/psi suppressions in minimum bias pA, AB (with light projectile), and Pb + Pb collisions at 200 A GeV/c. However the impact parameter (ET) dependence of the J/psi suppress ion factor, both, in S + U and Pb + Pb reactions at 200 A GeV/c and 158 A G eV/c, respectively, is not well reproduced. We also tested the additional m echanism of the energy degradation of leading particles, with which both, t he normal and anomalous J/psi suppressions in minimum bias pA, AB, and Pb Pb collisions and the E-T dependence of the J/psi suppression factor are b etter reproduced.