Drell-Yan and J/psi production in high energy proton-nucleus and nucleus-nucleus collisions

The distributions of outgoing protons and charged hadrons in high energy pr oton-nucleus collisions are described rather well by a linear extrapolation from proton-proton collisions. This linear extrapolation is applied to pre cisely measured Drell-Yan cross sections for 800 GeV protons incident on a variety of nuclear targets. The deviation from linear scaling in the atomic number A can be accounted for by energy degradation of the proton as it pa sses through the nucleus if account is taken of the time delay of particle production due to quantum coherence. We infer an average proper coherence t ime of 0.4+/-0.1 fm/c. Then we apply the linear extrapolation to measured J /psi production cross sections for 200 and 450 GeV/c protons incident on a variety of nuclear targets. Our analysis takes into account energy loss of the beam proton, the time delay of particle production due to quantum coher ence, and absorption of the J/psi, On nucleons. The best representation is obtained for a coherence time of 0.5 fm/c, which is consistent with Drell-Y an production, and an absorption cross section of 3.6 mb, which is consiste nt with the value deduced from photoproduction of the J/psi on nuclear targ ets. Finally, we compare to recent J/psi, data from S+U and Pb+Pb collision s at the SPS. The former are reproduced reasonably well with no new paramet ers, but not the latter.