Updated analysis of jet quenching at RHIC and LHC within the light cone path integral approach

Abstract

We present results of a detailed analysis of experimental data on the nuclear modification factor R AA and the flow coefficient v 2 for light hadrons from RHIC for 0.2 TeV Au + Au collisions and from LHC for 2.76 and 5.02 TeV Pb + Pb, and 5.44 TeV Xe + Xe collisions. We perform calculations within the light-cone path integral (LCPI) approach to induced gluon emission. We use running α s which is frozen at low momenta at some value α s f r . We find that the RHIC data support somewhat larger value of α s f r . For the χ 2 optimized values of α s f r , the theoretical predictions are in reasonable agreement with data on R AA and v 2. Calculations made for different formation times and life-times of the QGP show that jet quenching at the RHIC and LHC energies is only weakly sensitive to the initial and final stages of the QCD matter evolution.

Medium induced QCD cascades: broadening and rescattering during branching

“…Experimentally, the broadening is rather small and its observation at the LHC energies is hindered by the vacuum effects [31,32]. There are also possible effects which could give negative contribution to the broadening [33][34][35]. Furthermore, a more realistic model of the medium accounting for its expansion [34,36,37] will probably reduce the amount of the broadening.…”

Jet quenching from heavy to light ion collisions

“…In the present work, by fixing free parameters from fitting available data on R AA for heavy ion collisions, we perform calculations of the nuclear modification factor for 0.2 and 7 TeV O+O collisions for scenarios with and without mQGP formation in pp collisions (we will often omit for clarity adding "in pp collisions"), and for an intermediate scenario when mQGP is formed only in pp collisions at the LHC energies. We use the jet quenching model of [32] (with some improvements made in [11]), based on the LCPI approach [3] to induced gluon emission. We perform calculations of the radiative energy loss using the method suggested in [33], which allows to account for accurately the Coulomb effects in multiple parton scattering.…”

“…An important feature of our calculations is that we use a temperature dependent parametrization of the running α s (suggested in [34]). In [34] it was demonstrated that the T -dependent QCD coupling largely solves the problem of JHEP09(2021)087 difference between the optimal values of α s for the RHIC and LHC energies [11,35]. Use of the T -dependent QCD coupling allows to avoid the ambiguities for small systems (pp and light ion collisions) connected with the choice of α s for large and small size QGP, because the parameters, fitted to data for heavy ion collisions, automatically fix α s for small size QGP.…”

“…Our theoretical scheme for calculation of the medium modification factors is similar to the one used in our previous jet quenching analyses (see [11,30,32,34]). For this reason, here we only outline its main aspects.…”

“…In this scenario, with the Glauber initial conditions for the QGP fireball at the proper time τ 0 ∼ 0.5 fm, one can obtain within pQCD jet quenching models rather good description of the available data on the nuclear modification factor from RHIC for Au+Au collisions and from LHC for Pb+Pb and Xe+Xe JHEP09(2021)087 collisions (see, e.g., refs. [7][8][9][10][11]). However, it is possible that the assumption that QGP is not formed in pp collisions is not valid.…”