Abstract

We study the path length dependence of energy-loss in the Quark Gluon Plasma (QGP) by measuring the azimuthal anisotropy coefficient and transverse momentum ( $p_{\mathrm{T}}$ ) spectra for charged hadrons in Au + Au at $\sqrt{s_{NN}}$ = 200 $\mathrm{GeV}$ at the RHIC-PHENIX experiment. To estimate the strength of the energy-loss as a function of $p_{\mathrm{T}}$ , we use the $\Delta p_{\mathrm{T}}$ which is the difference of $p_{\mathrm{T}}$ which provide the same yields at in-plane and out-of-plane directions. The results indicate that there are different structures between low- $p_{\mathrm{T}}$ and high- $p_{\mathrm{T}}$ regions. At high- $p_{\mathrm{T}}$ , the size of $\Delta p_{\mathrm{T}}$ increases as the centrality goes up. We also calculate the difference of the path length of in-plane and out-of-plane directions for each centrality. The difference of the path length increases along with the centrality and the tendency is the same with the $\Delta p_{\mathrm{T}}$ results.