Jet quenching test of the QCD matter created at RHIC and the LHC needs opacity-resummed medium induced radiation

Abstract

After almost two decades of investigation, jet quenching has become a fundamental tool to study the properties of the QCD matter produced in high-energy nuclear collisions. Despite the large progress in both experimental and theoretical tools, several unknowns remain to be solved. In particular the systematics of the QCD matter parameters extracted at different energies and centralities is still puzzling. On the other hand, a lot of attention has been put in the last few years to a correct resummation of the multiple scatterings that the particles of the jet suffer when traversing the QCD matter. Present formalisms have substantially improved the multiple-soft or single hard scattering approximations, common in the last twenty years. We show here that medium parameters extracted with full resummed medium-induced gluon radiation spectra significantly differ from these two extreme approximations, providing natural systematics for different collision energies and centralities, with no inconsistencies. For the case of the full resummation this ensures that the density of scattering centers as a function of the temperature qualitatively agrees with the equation of state computed in lattice QCD.