Quenching of Hadron Spectra in Heavy Ion Collisions at the LHC

Abstract

The $p_\perp$ dependence of the nuclear modification factor $R_{\rm AA}$ measured in PbPb collisions at the LHC exhibits a universal shape, which can be very well reproduced in a simple energy loss model based on the BDMPS medium-induced gluon spectrum. The scaling is observed for various hadron species ($h^\pm$, $D$, $J/\psi$) in different centrality classes and at both colliding energies, $\sqrt{s}=2.76$ TeV and $\sqrt{s}=5.02$ TeV. Results indicate an 10-20% increase of the transport coefficient from $\sqrt{s}=2.76$ TeV to $\sqrt{s}=5.02$ TeV, consistent with that of particle multiplicity. Based on this model, a data-driven procedure is suggested, which allows for the determination of the first and second moments of the quenching weight without any prior knowledge of the latter.