Scaled momentum distributions for K _S ⁰ and ∧/∧ in DIS at HERA

Scaled momentum distributions for the strange hadrons K _S ⁰ and ∧/∧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 GeV ² 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. Nextto-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 _S ⁰ and ∧/∧ strange hadrons.