Measurement of parton distributions of strange quarks in the nucleon from charged-kaon production in deep-inelastic scattering on the deuteron

The momentum and helicity density distributions of the strange quark sea in the nucleon are obtained in leading order from charged-kaon production in deep-inelastic scattering on the deuteron. The distributions are extracted from spin-averaged K±K± multiplicities, and from K±K± and inclusive double-spin asymmetries for scattering of polarized positrons by a polarized deuterium target. The shape of the momentum distribution is softer than that of the average of the u¯ and d¯ quarks. In the region of measurement 0.021.0 GeV2Q2>1.0 GeV2, the helicity distribution is zero within experimental uncertainties.