Jet peak shapes based on two-particle angular correlations in lead-lead collisions at $\sqrt{{s_{\mathrm{NN}}}}$ = 5.02 TeV

TL;DR

This study investigates how jet peak shapes in two-particle correlations evolve in lead-lead collisions at 5.02 TeV, revealing broadening and asymmetry changes related to collision centrality and particle pseudorapidity.

Contribution

It provides the first detailed analysis of the longitudinal invariance and shape evolution of jet peaks in heavy-ion collisions at this energy, highlighting medium effects on jet structures.

Findings

Jet peaks broaden in pseudorapidity and azimuth with increasing collision overlap.

Broadening in pseudorapidity is more pronounced than in azimuth.

Longitudinal asymmetry increases with higher pseudorapidity.

Abstract

The longitudinal invariance of jet-induced peaks in two-particle correlation functions from relativistic lead-lead collisions is experimentally explored. The data were collected at a center-of-mass energy per nucleon pair of 5.02 TeV in 2018 using the CMS detector. The dataset corresponds to an integrated luminosity of 0.607 nb$^{-1}$. Long- and short-range correlations are studied through two-dimensional distributions of the separations in pseudorapidity and azimuth between particles in an event. Jets manifest as a well-defined peak at small angular separations, and the shape of this peak provides insight into jet medium interactions. This Letter examines the evolution of the jet peak shape, focusing on the dependence of its width and longitudinal asymmetry on the transverse momentum, collision centrality, and pseudorapidity of the associated charged particles. The jet-peak distributions of lower transverse momentum particles broaden in both pseudorapidity and azimuth with increasing collision overlap, with the broadening in pseudorapidity being more pronounced. The longitudinal asymmetry of the peaks is also found to increase as the average pseudorapidity increases. These results are compared to proton-proton collision data that were obtained at the same nucleon-nucleon collision center-of-mass energy with an integrated luminosity of 252 nb$^{-1}$.