Detail study of the medium created in Au+Au collisions with high $p_T$   probes by the PHENIX experiment at RHIC
  Recent results on high $p_T$ identified hadrons in Au+Au collisions from the PHENIX experiment are presented. The $R_{\rm AA}$ for $\pi^0$ and $\eta$ are found to be very consistent. The second and fourth order collective flow of $\pi^0$s have been measured and found that $v_4/v_2^2$ is consistent with the one observed in lower $p_T$ region. Assuming the suppression of the $\pi^0$ yield at highest $p_T$ arises from energy loss of partons, we found that the energy loss is $L^3$ dependent, where $L$ is the path length of the partons in the medium. The $\delta p_T/p_T$'s of high $p_T$ hadrons are computed from 39GeV Au+Au over to 2.76TeV Pb+Pb, and found that they vary by a factor of six. We have seen a smooth trend in $\delta p_T/p_T$ from RHIC energy to LHC energy when plotting against charged multiplicity of the systems. 
Takao Sakaguchi (for the PHENIX collaboration)
nucl-ex hep-ex