Nuclear Transverse Momentum Distributions For Multiple Scattering Effects In The Drell-yan Process

Anomalous A-dependence has been observed in high tranverse momentum( qt ) production of hadrons. It has been argued that such effect ,i.e. a nuclear dependence of the qt distributions, should also occur for high-mass pairs produced in nuclear Drell-Yan process.In 1987, The NA10 Collaboration in CERN present the first clear evidence for a nuclear dependence of the transverse momentum distribution of massive muon pairs produced in hadronic interactions. Comparing the cross-section for high mass dimuon production by incident negative pions (140 and 286 GeV) off tungsten and deuterium, it was found that their ratio increases with the dimuon transverse momentum. The difference of the mean transverse momentum squared △ < q12 > was measured in different nuclear Drell-Yan processes. In 1991 , the FNAL E772 extended the nuclear dependence measurements by determining △ < qt2 > for Drell-Yan production for a series of nuclei. These experimental results show that △ is independent of the dimuon mass and logitudinal momentum, and imply the scattering of the incident quark within the target nucleus.By means of the Glauber model , the difference of the mean transverse momentum squared △ < qt2 > is studied for the dependence of the incident proton energy and nucleus. The theoretical results are in good agreement with the FNAL E772 experimental data.