Experimental determination of the antiproton structure function by the Drell-Yan mechanism

We present results on the measurement of the Drell-Yan absolute cross section and of the shape of the nucleon structure functions by the analysis of massive dimuon events produced by antiprotons at 150 GeV and by protons at 150 and 200 GeV. Good agreement is found with the results of the neutrino deep inelastic scattering (DIS) experiments, for the shape of the valence structure function. The measured cross section however, when compared to the model predictions assuming the DIS nucleon structure function exhibits a normalization factor K = 2.3 +- 0.4. (orig.)