Multiplicities of charged kaons from deep-inelastic muon scattering off an isoscalar target

Abstract Precise measurements of charged-kaon multiplicities in deep inelastic scattering were performed. The results are presented in three-dimensional bins of the Bjorken scaling variable x , the relative virtual-photon energy y , and the fraction z of the virtual-photon energy carried by the produced hadron. The data were obtained by the COMPASS Collaboration by scattering 160  GeV muons off an isoscalar 6 LiD target. They cover the kinematic domain 1 ( GeV / c ) 2 Q 2 60 ( GeV / c ) 2 in the photon virtuality, 0.004 x 0.4 , 0.1 y 0.7 , 0.20 z 0.85 , and W > 5  GeV / c 2 in the invariant mass of the hadronic system. The results from the sum of the z -integrated K + and K − multiplicities at high x point to a value of the non-strange quark fragmentation function larger than obtained by the earlier DSS fit.