J/psi production in an equilibrating partonic system

Any color singlet or octet c (c) over bar pair is created at short distance s and then expands to a full size of J/psi. Such a dynamical evolution proc ess is included here in calculations for the J/psi number distribution as a function of transverse momentum and rapidicy in central Au-Au collisions a t both RHIC and LHC energies. The c (c) over bar pairs are produced in the initial collision and in the partonic system during the prethermal and ther mal stages through the partonic channels ab --> c (c) over bar[L-2S+1(J)] a nd ab --> c (c) over bar[L-2S+1(J)]x, and then they dissociate in the latte r two stages. Dissociation of c (c) over bar in the medium occurs via two r eactions: (a) color singlet c (c) over bar plus a gluon turns to color octe t c (c) over bar, (b) color octet c (c) over bar plus a gluon persists as c olor octet. There are modest yields of c (c) over bar in the prethermal sta ge at RHIC energy and through the reactions ab --> c (c) over bar[L-2S+1(J) ] at LHC energy for partons with large average momentum in the prethermal s tage rat both collider energies and in the thermal stage at LHC energy. Pro duction from the partonic system competes with the suppression of the initi al yield in the deconfined medium. Consequently, a bulge within -1.5 < y < 1.5 has been found for the J/psi number distribution and the ratio of J/psi number distributions for Au-Au collisions to nucleon-nucleon collisions. T his bulge is caused by the partonic system and is thus an indicator of a de confined partonic medium. Based on this result we suggest the rapidity regi on worth measuring in future experiments at RHIC and LHC to be -3 < y < 3. (C) 1999 Elsevier Science B.V. All rights reserved.