  One of the primary aims of the ongoing nuclear collisions at Relativistic
Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies is to create
a Quark Gluon Plasma (QGP). The heavy quarks constitutes a unique probe of the
QGP properties. Both at RHIC and LHC energies a puzzling relation between the
nuclear modification factor $R_{AA}(p_T)$ and the elliptic flow $v_2(p_T)$
related to heavy quark has been observed which challenged all the existing
models.\\ We discuss how the temperature dependence of the heavy quark drag
coefficient can address for a large part of such a puzzle. We have considered
four different models to evaluate the temperature dependence of drag and
diffusion coefficients propagating through a quark gluon plasma (QGP). All the
four different models are set to reproduce the same $R_{AA}(p_T)$
experimentally observed at RHIC energy. We have found that for the same
$R_{AA}(p_T)$ one can generate $2-3$ times more $v_{2}$ depending on the
temperature dependence of the heavy quark drag coefficient.
