Medium modification of the charge-weighted Energy-Energy Correlators in Pb+Pb collisions at $\sqrt{s_{NN}}=5.02$~TeV

TL;DR

This paper investigates medium-induced modifications to charge-dependent jet substructure using charged-weighted Energy-Energy Correlators (EEC) in p+p and 0-10% Pb+Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV. It establishes a p+p baseline via PYTHIA and then predicts Pb+Pb modifications with the SHELL model, linking energy loss, medium response, and hydrodynamics to observable charge correlations across jet flavors. A universal A+A/p+p modification pattern emerges, with jet quenching enhancing opposite-charge correlations at small angles while suppressing them at large angles, and a distinctive V-shaped modification in the opposite-charge channel attributed to enhanced energy weighting at small $R_L$. Factorization of the EEC into charged-hadron pair multiplicity and energy weighting clarifies the origin of these features and supports the utility of charge-sensitive correlators for constraining hadronization and jet-quenching dynamics in the quark-gluon plasma.

Abstract

We present a systematic study of medium-induced modifications in charge-dependent jet substructure using the charge-weighted Energy-Energy Correlators (EEC) in p+p and 0-10\% central Pb+Pb collisions at a center-of-mass energy of 5.02 TeV. Charged hadron jets as well as flavor separated quark and gluon-initiated jets with momentum 40-60 GeV and R=0.4 are analyzed. The ratio of the charge-weighted distribution to the inclusive EEC, which reflects the magnitude of charge correlations, is consistently negative, demonstrating the dominance of opposite-charge pairs due to charge conservation. In Pb+Pb collisions, significant medium modifications are observed. The A+A to p+p ratio for charge correlations exhibits a universal pattern across jet types, showing no flavor dependence. Jet quenching enhances opposite-charge correlations at small angles while reducing them at large angles, leading to a steeper angular distance RL dependence of charge correlations in A+A, indicating a more rapid decorrelation behavior as RL increases. A distinctive V-shaped modification pattern appears in the plateau-like enhancement in the transition and small-RL region, independent of jet flavor. Through factorization of the EEC into charged hadron pair multiplicity and average energy weighting distributions, we identify enhanced energy weighting of opposite-charge pairs at small RL as the origin of the V-shaped modification. Also, the plateau-like enhancement of charge correlations is found to be unrelated to selection bias effects.

Figures (6)

• Figure 1: PYTHIA8 simulation results of normalized charge-weighted EEC with its like- (opposite-) charge components (upper panel) and charge-weighted EEC/inclusive EEC ratio distributions (bottom panel) as functions of $R_{\rm L}$ for inclusive charged jets with a jet size of $R=0.4$ produced in $\rm p+p$ collisions at $\sqrt{s}=200$ GeV(left panel) and $\sqrt{s}=5.02$ TeV(right panel). The results are compared with the STAR STAR:2025jut and ALICE experimental data C3NT2024, respectively.
• Figure 2: Charge-weighted EEC in p+p and central $(0-10\%)$ Pb+Pb collisions and their A+A/p+p ratios distributions as functions of $R_\text{L}$ for inclusive charged, gluon and quark jets with a radius of $R=0.4$ in jet $p_{\rm T}$ interval $40-60$ GeV at $\sqrt{s}=5.02$ TeV.
• Figure 3: Like and opposite components of EEC in p+p and central $(0-10\%)$ Pb+Pb collisions and their A+A/p+p ratios distributions as functions of $R_\text{L}$ for inclusive charged jets with a radius of $R=0.4$ at $\sqrt{\rm s}=5.02$ TeV in jet $p_{\rm T}$ interval $40-60$ GeV.
• Figure 4: Number of jets normalized pair-number distributions (upper panel) and averaged energy weight (lower panel) distributions of like and opposite components EEC in p+p and central $(0-10\%)$ Pb+Pb collisions and their A+A/p+p ratios distributions as functions of $R_\text{L}$ for inclusive charged jets with a radius of $R=0.4$ at $\sqrt{\rm s}=5.02$ TeV in jet $p_{\rm T}$ interval $40-60$ GeV.
• Figure 5: Charge weighted EEC/inclusive EEC ratios in p+p and central $(0-10\%)$ Pb+Pb collisions and their A+A/p+p ratios distributions as functions of $R_{L}$ for inclusive charged, gluon and quark jets with a radius of $R=0.4$ in jet $p_{\rm T}$ interval $40-60$ GeV at $\sqrt{s}=5.02$ TeV.