Study of medium modified jet shape observables in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV using EPOS and JEWEL event generators

Abstract: The jet-medium interaction in high energy heavy ion collisions is an important phenomena to characterize the hot and dense medium produced in such collisions. The study of medium-induced modifications to the substructure of inclusive charged jets indicates a redistribution of energy inside the jet cone and provides insight into the energy loss mechanisms of jets in the medium. We investigate the in-medium modification to two jet shape observables i.e., the differential jet shape ($\rho$(r)) and the angularity (g) in the most central $Pb-Pb$ collisions at $\sqrt{s_{NN}} ~=~ 2.76$ TeV using two commonly used event generators i.e., JEWEL (recoil OFF) and EPOS-3 in the jet-p$_T$ range of 20-40 GeV/c. JEWEL with recoil OFF has been used primarily as a reference system as that has been found to explain the global jet observables satisfactorily but lacks in jet-shape variables at higher jet-radii. EPOS-3 that explains the bulk properties in such collisions quite well takes into account a hydrodynamically evolving bulk matter, jets and hard-soft interactions. A comparison between the results from these models shows that while JEWEL (recoil OFF) does not explain the distribution of lost energy at higher radii with respect to the jet-axis, EPOS-3 explains the effect quite well. However, in EPOS-3, the partonic energy loss mechanism and secondary hard-soft interactions during hadronization and hadronic cascade phase are different from the conventional jet energy loss models. The current study can, therefore, provide important new insights on mechanisms regarding the modeling of the medium and hard-soft interactions in heavy ion collisions.