High p_T Quarkonium production and propagation though the QGP

Melting of heavy quarkonium states like the J/ψ and the Upsilon mesons due to color screening as they propagate through a deconfined quark-gluon plasma (QGP) has been proposed as one of the principal signatures for its formation in heavy ion collisions. I will present a model of the propagation, assuming that the wavefunction of the quarkonia is not modified in the short time scale of formation, and the main effect of the thermal medium is inducing their dissociation via collision with thermal gluons. This model adequately describes quarkonium suppression at RHIC. The large suppression of high pT, prompt J/ψ in nucleus-nucleus collisions observed at the LHC suggests that thermal modification of the quarkonium wavefunction is necessary.