Soft QCD from ATLAS and CMS

TL;DR

This paper presents comprehensive measurements of hadron production, diffraction, and underlying event activity in proton-proton collisions at various energies, comparing results with QCD models to improve understanding of soft QCD processes.

Contribution

It provides new detailed experimental data on soft QCD phenomena in pp collisions at multiple energies, including diffraction and underlying event studies, with comparisons to Monte Carlo models.

Findings

Charged particle spectra and multiplicity distributions measured at different energies.

Diffractive and inelastic cross-sections quantified and analyzed.

Two-particle correlations and underlying event activity characterized.

Abstract

Measurements of hadron production in pp collisions by the ATLAS and CMS experiments are presented, including charged particle transverse momentum, pseudorapidity and event-by-event multiplicity distributions at sqrt(s) = 0.9, 2.36 and 7 TeV, for NSD and inelastic events. Diffraction is studied with either diffraction enriched or suppressed data samples. Total inelastic cross-section as well as gap cross-section measurements are shown. Measured spectra of identified strange hadrons, reconstructed based on their decay topology, are also discussed. Comparisons to several QCD Monte Carlo models and tunes are exhibited. Results on two-particle angular correlations over a broad range of pseudorapidity and azimuthal angle in pp collisions are presented. Underlying event activity are studied with different hard probes: tracks, trackjets, calorimeter clusters, or in Drell-Yan events.