The surprisingly transparent sQGP at LHC

We present parameter-free predictions of the nuclear modification factor, , of high pT pions produced in Pb + Pb collisions at and 5.5 ATeV based on the WHDG/DGLV (radiative + elastic + geometric fluctuation) jet energy loss model. The initial quark gluon plasma (QGP) density at LHC is constrained from a rigorous statistical analysis of PHENIX/RHIC π0 quenching data at and the charged particle multiplicity at ALICE/LHC at 2.76 ATeV. Our perturbative QCD tomographic theory predicts significant differences between jet quenching at RHIC and LHC energies, which are qualitatively consistent with the pT-dependence and normalization—within the large systematic uncertainty—of the first charged hadron nuclear modification factor, , data measured by ALICE. However, our constrained prediction of the central to peripheral pion modification, , for which large systematic uncertainties associated with unmeasured p + p reference data cancel, is found to be over-quenched relative to the charged hadron ALICE data in the range 5