Speaker
Description
The azimuthal anisotropy coefficient $v_2$ is a good tool to investigate
properties of the QGP not only to study collective flow, but also the energy loss of hard scattered partons. For non-central collisions,
the collision area has an elliptic shape. When the hard scattered partons
created in the collision are emitted, they have different path-lengths
interacting with QGP depending on the orientation with respect
to the reaction plane, azimuth, which results in the difference of the yields
of high transverse momentum ($p_T$) particles in in-plane and out-of-plane.
Therefore, the energy loss mechanism can be investigated by measuring
the $v_2$ at high $p_T$.
We have recently improved the precision of the $v_2$ measurement by
reducing background tracks using the silicon vertex tracker installed in
PHENIX. In this presentation, I discuss the collision centrality dependence
and $p_T$ dependence of charged hadron $v_2$ in Au+Au collisions
at ${\sqrt{s_{NN}}}$=200GeV from the data collected by PHENIX during the
RHIC Year-2011 run.
