Drell-Yan events from 400 GeV/c protons: Determination of theK-factor in a large kinematical domain

We present the analysis of ∼30,000 high mass dimuons (Mμμ>4.5 GeV/c2) produced in 400 GeV/c proton-platinum interactions. A determination of theK-factor is given for different values ofx F andMμμ, and its variations are compared to QCD predictions. The proton structure functions derived from these events are compared to the values obtained in deep inelastic lepton scattering.