Scaling properties of fractional momentum loss of high- pT hadrons in nucleus-nucleus collisions at sNN from 62.4 GeV to 2.76 TeV

Measurements of the fractional momentum loss (Sloss ≡ δpT /pT ) of high-transverse-momentum-identified hadrons in heavy-ion collisions are presented. Using π0 in Au + Au and Cu + Cu collisions at √sNN = 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 Sloss as a function of a number of variables: the number of participants, Npart, the number of quark participants, Nqp, the charged-particle density, dNch/dη, and the Bjorken energy density times the equilibration time, eBjτ0. We find that the pT , where Sloss has its maximum, varies both with centrality and collision energy. Above the maximum, Sloss tends to follow a power-law function with all four scaling variables. The data at √sNN = 200 GeV and 2.76 TeV, for sufficiently high particle densities, have a common scaling of Sloss with dNch/dη and eBjτ0, lending insight into the physics of parton energy loss.