Ground state correlations in Deep Inelastic Scattering and the

Such high energy processes as deep inelastic scattering (DIS) and Drell-Yan heavy lepton pair production are among the most important tools to probe the quark and gluon interaction. We calculated non-perturbative corrections to the LO cross section formulae for DIS and the Drell-Yan process. The interaction of partons was taken into account via dressing the incoming quark lines with spectral functions. We found that the effect of ground state correlation in DIS is large in the region of small Bjorken x and low momentum transfer Q 2. For a quark width of the order of 200 MeV, the cross section deviation reaches as much as 50% for Q 2 = 10 GeV 2. On the other hand, for the values of Q 2 well above the resonance region, e. g. 200 GeV 2 , the effect of the initial quark off-shellness turned out to be small in DIS, but still substantial for the triple differential Drell-Yan cross section. Semi-inclusiveness of the latter process opens a possibility to extract from the experimental data important information on the shape of the quark spectral function in the nucleon. From the comparison to the resent data on the Drell-Yan cross section from NuSea collaboration, we obtained for the width of the quark spectral function the value about 200 MeV. The performed off-shell DIS and Drell-Yan cross section calculations allow for a better understanding of the quark and gluon interaction in the nucleon and, thus, the nucleon structure. PACS. 13.60.Hb Total and inclusive cross sections (including deep-inelastic processes) – 13.85.Qk Inclusive production with identified leptons, photons, or other nonhadronic particles