Sensitivity of Pion versus Parton-Jet Nuclear Modification Factors to the Path-Length Dependence of Jet-Energy Loss at RHIC and LHC

TL;DR

This paper compares pion and parton-jet nuclear modification factors at RHIC and LHC, examining their sensitivity to jet-energy loss models and path-length dependence, revealing limitations in current models' ability to distinguish physics mechanisms.

Contribution

It provides a comparative analysis of pion and reconstructed jet nuclear modification factors, highlighting their differing sensitivities to jet-medium coupling and path-length dependence.

Findings

Both models need reduced jet-medium coupling from RHIC to LHC.

Reconstructed jets offer more information but are limited by superimposed effects.

Results are insensitive to jet-path dependence in the models studied.

Abstract

We compare the jet-path length and beam-energy dependence of the pion nuclear modification factor and a parton-jet nuclear modification factor at RHIC and LHC. We contrast predictions based on a linear pQCD and a highly non-linear hybrid-AdS holographic model of jet-energy loss. We find that both models require a reduction of the jet-medium coupling from RHIC to LHC to account for the measured pion nuclear modification factor. In case of the parton-jet nuclear modification factor, however, which serves as a lower bound for the LO jet nuclear modification factor of reconstructed jets, the extracted data can be characterized without a reduced jet-medium coupling at LHC energies. We conclude that while reconstructed jets are sensitive to both quarks and gluons and thus provide more information than the pion nuclear modification factor, their information regarding the jet-medium coupling is limited due to the superimposition with NLO and medium effects. Hence, a detailed description of the underlying physics requires both the leading hadron and the reconstructed jet nuclear modification factor. Unfortunately, the results for both the pion and the parton-jet nuclear modification factor are insensitive to the jet-path dependence of the models considered.