Charged-hadron suppression in Pb+Pb and Xe+Xe collisions measured with the ATLAS detector

TL;DR

This paper reports measurements of charged-hadron suppression in Pb+Pb and Xe+Xe collisions at the LHC, analyzing the nuclear modification factors to understand system-size effects in heavy-ion collisions.

Contribution

It provides new measurements of charged-hadron spectra and nuclear modification factors in Xe+Xe collisions, expanding the understanding of system-size dependence in heavy-ion physics.

Findings

Charged-hadron suppression varies with system size and centrality.

Nuclear modification factors differ between Pb+Pb and Xe+Xe collisions.

Results support models of energy loss in quark-gluon plasma.

Abstract

The ATLAS detector at the LHC recorded 0.49nb$^{-1}$ of Pb+Pb collisions and 25pb$^{-1}$ of $pp$ collisions, both at the center-of-mass energy 5.02TeV per nucleon pair. Recently, ATLAS also recorded 3$\mu$b$^{-1}$ of Xe+Xe collisions at the center-of-mass energy 5.44TeV, which provides a new opportunity to study the system-size dependence of the charged-hadron production in heavy-ion collisions. The large acceptance of the ATLAS detector allows to measure the spectra of charged hadrons in a wide range of pseudorapidity and transverse momentum. The nuclear modification factors $R_\mathrm{AA}$ are constructed as a ratio of the spectra measured in Pb+Pb or Xe+Xe collisions to that measured in $pp$ collisions. The $R_\mathrm{AA}$ obtained in the two systems are presented for different centrality intervals and the results are discussed.