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<100 GeV2 and the inelasticity 0.1<y<0.6. The K

0 and

production cross sections and their ratios are determined. K

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

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