N ov 2 01 7 Valence Quark and Gluon Distributions of Kaon from J / ψ Production

The only experimental information on the parton distribution of kaons was obtained from the scarce kaoninduced Drell-Yan cross section data. From these data, evidence for a valence u quark distribution of kaon softer than that of pion was found. We study the feasibility to extract kaon’s valence quark distribution via the existing kaon-induced J/ψ production data. We compare the NA3 data on the K−/π− and K/π ratios for J/ψ production on a platinum target with theoretical calculations based on the color-evaporation model. We show that the NA3 data on J/ψ production provide an independent evidence for a valence u quark distribution softer in kaon than in pion. The data also suggest different gluon distributions for kaon and pion.