Probing medium-induced jet splitting and energy loss in heavy-ion collisions

TL;DR

This paper investigates how jet splitting is modified by the quark-gluon plasma in heavy-ion collisions, revealing a non-monotonic energy dependence and explaining experimental puzzles at RHIC and LHC through a higher twist formalism.

Contribution

It introduces a model assuming coherent energy loss for jet subjets, explaining the energy-dependent nuclear modification of jet splitting functions and resolving the CMS-STAR groomed jet puzzle.

Findings

Non-monotonic jet energy dependence of nuclear modification observed.

Explains the difference in jet modification between RHIC and LHC.

Independent energy loss cannot fully account for observed modifications.

Abstract

The nuclear modification of jet splitting in relativistic heavy-ion collisions at RHIC and the LHC energies is studied based on the higher twist formalism. Assuming coherent energy loss for the two splitted subjets, a non-monotonic jet energy dependence is found for the nuclear modification of jet splitting function: strongest modification at intermediate jet energies whereas weaker modification for larger or smaller jet energies. Combined with the smaller size and lower density of the QGP medium at RHIC than at the LHC, this explains the CMS-STAR groomed jet puzzle -- strong nuclear modification of the momentum sharing $z_g$ distribution at the LHC whereas no obvious modification of the $z_g$ distribution at RHIC. In contrast, the observed nuclear modification pattern of the groomed jet $z_g$ distribution cannot be explained solely by independent energy loss of the two subjets. Our result may be tested in future measurements of groomed jets with lower jet energies at the LHC and larger jet energies at RHIC, for different angular separations between the two subjets.