Particle spectra at ZEUS

TL;DR

This paper investigates charged particle multiplicity distributions and spectra in deep inelastic ep scattering at HERA, comparing results with e+e- collisions, Monte Carlo models, and QCD predictions, revealing insights into particle production mechanisms.

Contribution

It provides new measurements of multiplicity distributions and scaled momentum spectra in DIS, and tests QCD-based models like MLLA and LPHD against experimental data.

Findings

KNO-scaling properties observed in data

Energy dependence of multiplicity distributions studied

Universal MLLA scale and LPHD parameters extracted

Abstract

Charged multiplicity distributions and the mean charged multiplicity have been investigated in inclusive neutral current deep inelastic ep scattering with the ZEUS detector at HERA using an integrated luminosity of 38.6 pb-1. The measurements were performed in the current region of the Breit frame, as well as in the current fragmentation region of the hadronic center-of-mass frame. The KNO-scaling properties of the data were investigated and the energy dependence of multiplicity distributions was studied using different energy scales. The data are compared to results obtained in e+e- collisions and to previous DIS measurements as well as to leading-logarithm parton-shower Monte Carlo predictions. The scaled momentum distributions of charged particles in jets have been also measured for dijet photoproduction with the ZEUS detector at HERA using an integrated luminosity of 359 pb-1. The distributions are compared to predictions based on perturbative QCD carried out in the framework of the modified leading-logarithmic approximation (MLLA) and assuming local parton-hadron duality (LPHD). The universal MLLA scale, Lambda_ eff, and the LPHD parameter, kappa^ch, are extracted.