Quantum effects in charmonium formation and signatures of a quark-gluon plasma

Abstract

We consider initial conditions of a heavy charmed quark-antiquark pair produced in a spacetime region whose size is much less than that of an isolated bound state. This situation is of Interest for studying the effects of a QCD plasma phase possibly produced in heavy-ion collisions at high energy. The time evolution of such a system is studied, assuming that the quarks initially propagate as free particles to simulate the screened potential in the plasma phase. Due to the small initial size of the quark wave packets, large relativistic momentum components play an important part in the evolved spatial distributions. This feature produces significant changes to the classical description of such systems in which sharp particle trajectories and formation times are employed. To highlight this difference, we use a simple one-dimensional model to follow the evolution of the system during the plasma phase alone. The results indicate that only when such a procedure is carried through the entire time history of the system using realistic physical parameters can one have confidence that experiments are revealing some signature of bound state formation which is characteristic of the existence of a plasma phase.