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 T ) spectra for charged hadrons in Au + Au at s N N = 200 GeV at the RHIC-PHENIX experiment. To estimate the strength of the energy-loss as a function of p T , we use the Δ p T which is the difference of p 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 T and high- p T regions. At high- p T , the size of Δ p 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 Δ p T results.
Scaling Properties of Azimuthal Anisotropy inAu+AuandCu+CuCollisions atsNN=200 GeV