Pseudorapidity distributions of charged hadrons in lead-lead collisions at $\sqrt{s_\mathrm{NN}}$ = 5.36 TeV

TL;DR

This paper reports the measurement of charged hadron pseudorapidity distributions in lead-lead collisions at 5.36 TeV, providing new insights into particle production at unprecedented energies and comparing results with models and previous data.

Contribution

First measurement of charged hadron pseudorapidity distributions at 5.36 TeV in lead-lead collisions using CMS detector, extending understanding of high-energy nuclear interactions.

Findings

Charged-hadron η density in central collisions is 2032 ± 91.

Results are consistent with extrapolations from lower energies.

Data agree with various Monte Carlo event generators.

Abstract

The pseudorapidity ($\eta$) distributions of charged hadrons are measured using data collected at the highest ever nucleon-nucleon center-of-mass energy of $\sqrt{s_\mathrm{NN}}$ = 5.36 TeV for collisions of lead-lead ions. The data were recorded by the CMS experiment at the LHC in 2022 and correspond to an integrated luminosity of 0.30 $\pm$ 0.03 $\mu$b$^{-1}$. Using the CMS silicon pixel detector, the yields of primary charged hadrons produced in the range $\vert\eta\vert$ $\lt$ 2.6 are reported. The evolution of the midrapidity particle density as a function of collision centrality is also reported. In the 5% most central collisions, the charged-hadron $\eta$ density in the range $\vert\eta\vert$ $\lt$ 0.5 is found to be 2032 $\pm$ 91 (syst), with negligible statistical uncertainty. This result is consistent with an extrapolation from nucleus-nucleus collision data at lower center-of-mass energies. Comparisons are made to various Monte Carlo event generators and to previous measurements of lead-lead and xenon-xenon collisions at similar collision energies. These new data detail the dependence of particle production on the collision energy, initial collision geometry, and the size of the colliding nuclei.