Manuscript Information Authors

[1]	Hanyuan Zhang, RDFZ Chaoyang Branch School, Beijing, China.
[2]	Wei Shi, School of Science, Tianjin University, Tianjin, China.

Abstract

The strong interactions and the deconfined properties have been hot research topics in the high energy nuclear theory. When two heavy nuclei are accelerated to nearly the speed of light and collide with each other, a lot of kinetic energy can be transformed into partons. The partons in a small volume can form an extremely hot medium, where quarks and gluons are not constrained in a small volume size of the nucleon. Instead, they evolve in a relatively larger volume. The small deconfined medium is just like our early universe after the big bang. The extremely hot medium will expand outside, and the lifetime of this medium is very small. It cannot be measured directly in experiments. The coupling strength of this new state of the medium is a difficult and important problem. The medium coupling strength is closely connected with the heavy quark energy loss. The heavy quarks including charm or bottom quarks carry large mass. They are coupled with the medium through color interactions. Due to the large mass, their evolutions in the thermal medium can be described by semi-classical theoretical models instead of quantum field theories. The acceleration and deceleration of heavy quarks in the expanding deconfined medium are studied in details in this work. The change of heavy quarks depends on the velocities and the lifetime of the hot medium. With the strong coupling between charm quarks and the quark gluon plasma (QGP), charm quarks can reach kinetic equilibrium. This work builds the theoretical models for charm accelerations in the expanding QGP. It can explain the connections between charm quark coupling strength and its momentum thermalizations. From the calculations, heavy quarks are strongly coupled with the medium, and mainly suffer energy loss in the early stage of the medium evolutions where the temperature is much higher. This means that heavy quarks can research kinetic thermalization in the early stage of two nuclear collisions.

Keywords

Heavy Ion Collisions, Heavy Quark Thermalization, Quark Gluon Plasma

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