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

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.