The quark-gluon plasma (QGP) produced in the relativistic heavy-ion
collisions (RHIC) has been widely studied in recent years, which would
be useful for understanding the formation of the early universe. After
the collision, the created quarks and gluons will be thermalized and
form the plasma with high temperature and large density. The small
viscosity implies that QGP may be strong coupling. When temperature
decreases, the QGP will undergo a phase transition and become weakly
coupled hadronic gas. Due to the different stages in the collision and
the non-perturbative property of QGP, the study of RHIC physics may be
challenging.
Heavy quarks have been adopted as a hard probe for the QGP properties
for a long time. Recent data from both RHIC and SPS experiments reveal
surprisingly large values of the elliptic flow v2 and surprisingly small
values of the nuclear modification factor RAA exhibited by D mesons,
indicating a much stronger interaction between charm quarks and the
medium than we expected. Therefore, it is of great interest to study the
dynamics of heavy quarks in an expanding QGP medium and verify whether
they indeed approach equilibrium on a timescale on the order of the
lifetime of QGP.
In this talk, we will firstly provide a brief introduction to RHIC
physics. And then introduce the main results of our recent research on
the thermalization process of charm quarks in infinite and finite QGP
matter in the framework of Langevin algorithm.