Charged-particle multiplicities in proton-proton collisions at $\sqrt{s}$ = 0.9 to 8 TeV

TL;DR

This paper presents a detailed analysis of charged-particle multiplicities and pseudorapidity densities in proton-proton collisions at energies from 0.9 to 8 TeV, using the ALICE detector to improve measurement precision.

Contribution

It introduces an improved track-counting algorithm and diffractive process measurements, enabling more precise multiplicity and pseudorapidity density results across multiple energies.

Findings

Higher precision in multiplicity measurements compared to previous studies.

Observation of KNO scaling in specific pseudorapidity intervals.

Comparison of experimental data with Monte Carlo models shows varying degrees of agreement.

Abstract

A detailed study of pseudorapidity densities and multiplicity distributions of primary charged particles produced in proton-proton collisions, at $\sqrt{s} =$ 0.9, 2.36, 2.76, 7 and 8 TeV, in the pseudorapidity range $|\eta|<2$, was carried out using the ALICE detector. Measurements were obtained for three event classes: inelastic, non-single diffractive and events with at least one charged particle in the pseudorapidity interval $|\eta|<1$. The use of an improved track-counting algorithm combined with ALICE's measurements of diffractive processes allows a higher precision compared to our previous publications. A KNO scaling study was performed in the pseudorapidity intervals $|\eta|<$ 0.5, 1.0 and 1.5. The data are compared to other experimental results and to models as implemented in Monte Carlo event generators PHOJET and recent tunes of PYTHIA6, PYTHIA8 and EPOS.