Universal scaling dependence of QCD energy loss from data driven studies

Abstract

In this paper we study the energy loss of jets in the QGP via the nuclear modification factor $R_{\textrm{AA}}$ for unidentified particles at high $p_{\textrm{T}}$ ($\gtrsim 10 \textrm{GeV}/c$) in and out of the reaction plane of the collision. We argue that at such a high $p_{\textrm{T}}$ there are no genuine flow effects and, assuming that the energy loss is only sensitive to initial characteristics such as the density and geometry, find that $R_{\textrm{AA}}$ depends linearly on the (RMS) length extracted from Glauber simulations. Furthermore we observe that for different centrality classes the density dependence of the energy loss enters as the square root of the charged particle multiplicity normalized to the initial overlap area. The energy loss extracted for RHIC and LHC data from the $R_{\textrm{AA}}$ is found to exhibit a universal behavior.