Flavor dependence of Energy-energy correlators

TL;DR

This paper studies how the energy-energy correlators (EECs) within jets depend on the flavor of the initiating parton, revealing flavor-dependent differences and their implications for understanding jet modifications in heavy-ion collisions.

Contribution

It provides a detailed analysis of flavor dependence of jet EECs, including predictions of how gluon and quark jets differ and how flavor composition changes affect medium modifications.

Findings

Gluon jets have broader EEC distributions than quark jets.

Flavor composition variations influence the EECs at different energies.

A reduction in gluon jet fraction in A+A collisions impacts EEC modifications.

Abstract

Energy-energy correlators (EECs) within high energy jets serve as a key experimentally accessible quantity to probe the scale and structure of the quark-gluon plasma (QGP) in relativistic heavy-ion collisions. The CMS Collaboration's first measurement of the modification to the EEC within single inclusive jets in Pb+Pb collisions relative to p+p collisions reveals a significant enhancement at small angles, which may arise from jet transverse momentum $p_T$ selection biases due to jet energy loss. We investigate the dependence of jet EECs on the flavor of the initiating parton. The EEC distribution of a gluon jet is broader and the peak of transition from perturbative to non-perturbative regime occurs at a larger angle than a quark jet. Such flavor dependence leads to the different EECs for $\gamma$-jets and single inclusive jets due to their different flavor composition. It is also responsible for a colliding energy dependence of EECs of single inclusive jets at fixed jet energy. We also investigate the impact of flavor composition variation on the $p_T$ dependence of the jet EEC. We further propose that a change in the gluon jet fraction in A+A collisions compared to p+p can also contribute to a non-negligible enhancement of the medium modified EEC at small angles. Using the \textsc{Jewel} model, we predict the reduction of the gluon jet fraction in A+A collisions and estimate its impact on the EEC.