Time structure of anomalous J/ψ and ψ′ suppression in nuclear collisions

The data for the mean squared transverse momentum 〈p2t〉(Et) as function of transverse energy Et of J/ψ and ψ′ produced in Pb–Pb collisions at the CERN-SPS are analyzed and it is claimed that they contain information about the time structure of anomalous suppression. A transport equation which describes transverse motion of J/ψ and ψ′ in the absorptive medium is proposed and solved for a QGP and a comover scenario of suppression. While the comover approach accounts for the data fairly well without adjusting any parameter, the fit to the data within the QGP scenario requires to assume anomalous suppression to become effective rather late, 3–4 fm/c after the nuclear overlap.