Scaled momentum distributions for K0s and Lambda/bar Lambda in DIS at HERA

TL;DR

This paper measures the scaled momentum distributions of K0s and Lambda/bar Lambda hadrons in deep inelastic scattering at HERA, revealing scaling violations and testing fragmentation models against experimental data.

Contribution

It provides new measurements of strange hadron distributions in DIS and compares them with various QCD-based fragmentation predictions, highlighting discrepancies and improvements.

Findings

Leading-log Monte Carlo models fit data well

NLO QCD with e+e- FFs fails to describe data

Global FFs improve agreement with measurements

Abstract

Scaled momentum distributions for the strange hadrons K0s and Lambda/bar Lambda were measured in deep inelastic ep scattering with the ZEUS detector at HERA using an integrated luminosity of 330 pb-1. The evolution of these distributions with the photon virtuality, Q2, was studied in the kinematic region 10<Q2<40000 GeV2 and 0.001<x<0.75, where x is the Bjorken scaling variable. Clear scaling violations are observed. Predictions based on different approaches to fragmentation were compared to the measurements. Leading-logarithm parton-shower Monte Carlo calculations interfaced to the Lund string fragmentation model describe the data reasonably well in the whole range measured. Next-to-leading-order QCD calculations based on fragmentation functions, FFs, extracted from e+e- data alone, fail to describe the measurements. The calculations based on FFs extracted from a global analysis including e+e-, ep and pp data give an improved description. The measurements presented in this paper have the potential to further constrain the FFs of quarks, anti-quarks and gluons yielding K0s and Lambda/bar Lambda strange hadrons.