New COMPASS results on kaon multiplicities from SIDIS

Abstract

Abstract Preliminary COMPASS results on kaon multiplicities produced in semi-inclusive deep inelastic scattering of 160 GeV muons off a pure proton target are presented. The results constitute a data set of more than 600 data points, covering a large x, Q 2 and z domain in a fine binning with W > 5GeV/c2. The results from the sum of the z-integrated multiplicities M(K+)+M(K−) are presented versus x and compared to earlier COMPASS results on a deuteron target and to other experiments. In addition, we show the K−/K+ as well as p ¯ /p multiplicity ratios measured for hadrons carrying a large fraction z of the virtual-photon energy, 0.5 < z < 1. The data were obtained using a 160 GeV muon beam and an isoscalar 6LiD target. For values of z larger than 0.8, the results contradict expectations obtained using the formalism of (next-to-) leading order perturbative quantum chromodynamics. In particular the data show a strong dependence upon the missing mass Mx , not expected from the calculations. The results suggest that additional corrections to the formalism may be required to take into account the phase space available for hadronization.