Testing pQCD and AdS/CFT Energy Loss at RHIC and LHC

TL;DR

This paper compares pQCD and AdS/CFT models of jet quenching at RHIC and LHC energies, showing pQCD describes light hadron suppression well, while AdS/CFT predictions for D mesons do not match current data.

Contribution

It provides a rigorous comparison of weak-coupling pQCD and strong-coupling AdS/CFT energy loss models against experimental data without free parameters.

Findings

pQCD model describes light hadron suppression and azimuthal anisotropy well

AdS/CFT drag model poorly predicts D meson suppression

D to B meson R_AA double ratio can distinguish medium coupling strength

Abstract

We compare calculations of jet quenching observables at sqrt s = 2.76 ATeV to preliminary LHC data from weak-coupling pQCD and strong-coupling AdS/CFT drag energy loss models. Rigorously constrained to sqrt s = 200 AGeV RHIC pi^0 suppression data and introducing no free parameters, the pQCD-based WHDG model simultaneously describes qualitatively the suppression of light hadrons and quantitatively the azimuthal anisotropy (over many centrality classes) of light hadrons and the suppression of D mesons at LHC. The drag predictions shown here--qualitatively constrained to RHIC data--compare poorly to the measured suppression of D mesons, but the current experimental uncertainties are large. The double ratio of D to B meson R_AA(p_T) should provide a robust experimental measurement to distinguish between the very different assumptions of the strength of interactions in the QGP produced in heavy ion collisions; i.e., whether, from a jet quenching standpoint, the medium is either weakly- or strongly-coupled.