In this work heavy flavor production in ultrarelativistic heavy ion collisions is discus sed. The experiments at the Relativistic Heavy Ion Collider in Brookhaven National
Laboratory enabled to study the properties of nuclear matter under conditions of high
temperature and energy density, where the phase transition to a new state of matter,
Quark Gluon Plasma was theoretically predicted. There are several experimental tools
to uncover the characteristics of this matter. Here we focus on observables related to
charm and bottom quarks. These quarks are produced in early phase of the collisions
and therefore are sensitive to all phases of system evolution. The measurement of he avy quark production in p+p collisions is an important test of perturbative Quantum
Chromodynamics calculations and also a baseline for heavy ion measurements. The
charmonium plays very special role in the heavy ion collisions while suppression of
its production in heavy ion collisions is expected due to temperature sensitive Debye
color screening. While nuclear modification factor is essential to understand the energy
loss of heavy quarks in hot and dense matter the measurements of hydrodynamic flow
are an additional constraint and can be related to speed of system thermalization.
Results discussed here from the STAR experiment show that perturbative Quantum
Chromodynamics is well describing charm production in p+p collisions and nuclear
modification of charm mesons indicate that energy loss might be similar to tha of light
quarks. Surprisingly the flow of J/ψ is consistent with no flow at low transverse mo mentum and J/ψ polarization in helicity frame indicates a trend towards longitudinal
polarization as pT increases. Recent preliminary measurements using information from
the STAR Heavy Flavor Tracker confirm the previous results and in addition provide
access to new type of studies. In near future, the Beam energy scan program of STAR
will focus on determination of the critical point of phase diagram of nuclear matter
and the onset of Quark Gluon Plasma signals.
