J/ψ transverse momentum distribution in high energy nuclear collisions

The transverse momentum (pt) dependence of J/ψ production in heavy ion collisions is investigated in a transport model with both initial production and continuous regeneration of charmonia. The competition between the two production mechanisms results in a pt suppression in central collisions, the gluon multi-scattering in the initial stage leads to a high pt enhancement, and the regeneration populates J/ψs at low pt region and induces a minimum in RAA(pt). These three phenomena are indeed observed in both 200 GeV Cu + Cu and Au + Au collisions at RHIC energy.