Scaling properties of fractional momentum loss of high-pT hadrons in nucleus-nucleus collisions at $\sqrt{s_{{}_{NN}}}$ from 62.4 GeV to 2.76 TeV

Abstract

Measurements of the fractional momentum loss ($S_{\mathrm{loss}}\equiv \delta p_T/p_T$) of high-transverse-momentum-identified hadrons in heavy ion collisions are presented. Using ${\pi }^0$ in Au$+$Au and Cu$+$Cu collisions at $\sqrt{s_{{}_{NN}}}=62.4$ and 200 GeV measured by the PHENIX experiment at the Relativistic Heavy Ion Collider and and charged hadrons in Pb$+$Pb collisions measured by the ALICE experiment at the Large Hadron Collider, we studied the scaling properties of $S_{\mathrm{loss}}$ as a function of a number of variables: the number of participants, $N_{\mathrm{part}}$, the number of quark participants, $N_{\mathrm{qp}}$, the charged-particle density, $d{N}_{\mathrm{ch}}/d\eta$, and the Bjorken energy density times the equilibration time, ${\epsilon }_{\mathrm{Bj}}{\tau }_0$. We find that the $p_T$ where $S_{\mathrm{loss}}$ has its maximum, varies both with centrality and collision energy. Above the maximum, $S_{\mathrm{loss}}$ tends to follow a power-law function with all four scaling variables. The data at $\sqrt{s_{{}_{NN}}}$=200 GeV and 2.76 TeV, for sufficiently high particle densities, have a common scaling of $S_{\mathrm{loss}}$ with $d{N}_{\mathrm{ch}}/d\eta$ and ${\epsilon }_{\mathrm{Bj}}{\tau }_0$, lending insight on the physics of parton energy loss.

630 authors, 21 pages, 16 figures, 7 tables. v2 is version accepted by Phys. Rev. C. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.html