Article

Strangeness production at low Q2 in deep-inelastic ep scattering at HERA

Inter-University Institute for High Energies ULB-VUB Brussels Belgium; Universiteit Antwerpen Antwerpen Belgium
European Physical Journal C (Impact Factor: 5.25). 61(2):185-205. DOI: 10.1140/epjc/s10052-009-0995-1

ABSTRACT The production of neutral strange hadrons is investigated using deep-inelastic scattering events measured with the H1 detector
at HERA. The measurements are made in the phase space defined by the negative four-momentum transfer squared of the photon
2<Q
2<100 GeV2 and the inelasticity 0.1<y<0.6. The K

s
0 and

\varLambda([`\varLambda])\varLambda(\bar{\varLambda})
production cross sections and their ratios are determined. K

s
0 production is compared to the production of charged particles in the same region of phase space. The Λ–

[`\varLambda]\bar{\varLambda}
asymmetry is also measured and found to be consistent with zero. Predictions of leading order Monte Carlo programs are compared
to the data.

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    ABSTRACT: Scaled momentum distributions for the strange hadrons $ K_{\text{S}}^0 $ 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, Q 2, was studied in the kinematic region 10 < Q 2 < 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 $ K_{\text{S}}^0 $ and $ \Lambda /\bar{\Lambda } $ strange hadrons.
    Journal of High Energy Physics 03/2012; 2012(3). · 5.62 Impact Factor