Signatures of Absorption Mechanisms for J/psi and psi' Production in High-Energy Heavy-Ion Collisions

摘要

J/psi and psi' produced in high-energy heavy-ion collisions are absorbed bytheir collisions with nucleons and produced soft particles, leading to twodistinct absorption mechanisms. The signature of absorption by produced softparticles, as revealed by psi' production data, consists of a gap and a changeof the slope in going from the pA line to the nucleus-nucleus line when we makea semi-log plot of the survival probability as a function of the path length.Using this signature, we find from the J/psi production data in pA, O-Cu, O-U,and S-U collisions that the degree of J/psi absorption by produced softparticles is small and cannot account for the J/psi data in Pb-Pb collisions.The anomalous suppression of J/psi production in Pb-Pb collisions can beexplained as due to the occurrence of a new phase of strong J/psi absorption,which sets in when the local energy density exceeds about 3.4 GeV/fm^3. Toprobe the chemical content of the new phase, we propose to study the abundanceof open-charm mesons and charm hyperons which depends sensitively on the quarkchemical potential.