Inclusive and multiplicity-dependent pseudorapidity densities of charged particles in pp collisions at $\mathbf{\sqrt{s} = 13.6}$ TeV

TL;DR

This paper measures the distribution and multiplicity dependence of charged particles in proton-proton collisions at 13.6 TeV, providing new insights into particle production at the highest LHC energies.

Contribution

It presents the first detailed measurement of pseudorapidity densities and their multiplicity dependence at 13.6 TeV using upgraded detector systems.

Findings

Average pseudorapidity density at midrapidity is 7.10.

Results follow a power-law scaling with energy.

Provides a new reference for high-energy proton-proton collisions.

Abstract

The distribution of the pseudorapidity density of primary charged particles (${\rm d}N_{\rm ch}/ {\rm d}\eta$) in $|\eta|<1.5$ is measured in pp collisions at a center-of-mass energy of 13.6 TeV using the ALICE detector. Tracks are reconstructed with the upgraded Inner Tracking System and Time Projection Chamber, and results are reported for the INEL$>$0 event class (events having at least one charged particle in $|\eta|<1$). The multiplicity dependence of the pseudorapidity density of charged particles is also explored with the multiplicity determined by the forward detectors. The average charged-particle pseudorapidity density at midrapidity ($|\eta|<0.5$) is measured to be $\langle \mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta \rangle = 7.10 \pm 0.18$. Combined with lower-energy measurements, the INEL$>$0 results follow a power-law scaling with the center-of-mass energy. These measurements provide a new reference for charged-particle production at the highest proton$-$proton collision energy available at the LHC.