When does anomalous J/ψ suppression happen in nuclear collisions?

摘要

The data for _t~2>(E_t) of J/ψ produced in Pb-Pb collisions at the CERN-SPS contain information about when anomalous suppression is active. A general transport equation which describes transverse motion of J/ψ in the absorptive medium is proposed and solved for a QGP and a comover scenario of suppression. While inconsistencies appear in the QGP, the comover approach accounts for the data fairly well. For central collisions the bulk of anomalous suppression happens rather late, 3-4 fm/c after the nuclear overlap.