K-factor For Drell-Yan Process In Nucleus-Nucleus Collision And Nuclear Effect

With the purpose of investigating physical mechanism in the high energy A-A collision Drell-Yan process and EMC effect, we perform the computation on the K factor of the A-A collision by considering QCD as -order modification for Drell-Yanprocess. The actual reaction cross section for the Drell-Yan process should be the common Drell-Yan cross section multiplied by this K factor so as to account for the main corrections due to Annihilation diagrams and Compton diagrams. Using the perturbation QCD, Double ^-rescaling model, generalized x-rescaling model we analyze the K factor's nonconstancy problem for A-A collision. It is found that for the given momentum fraction x\ carried by the quark(anti-quark) or gluon within the bound nucleon the K factor's value is dependent upon the changing momentum fraction KI carried by the parton participating in annihilating into y ; that is to say K factor could not be regarded as a constant of near 2.In Fermi Lab. E772 cooperation group proved that there exists nuclear shadowing effect in Drell-Yan cross-section in different nuclear targets. Nuclear shadowing effect was also observed in the label-irrelevant region and in the measurement of nuclear target deep inelastic EMC effect. In terms of an empirical nuclear shadowing factor Ha, we calculate the K factor for Au-Au collision at energyv5 = 60, 130, 200GeV respectively and investigate p-C, C-C, Au-Au collision atenergy v5= 60 and 630 GeV for comparisons with or without the K factor. Theresults show that the K values have obviously bouncing behavior in the small x region when considering nuclear shadowing effect. The value of K will become smaller for the same nucleus when energy gets higher. The heavier the nucleus, the smaller the K's value. Nuclear shadowing effect in small x region may be one reason fornonconstancy of the K factor.We estimate further the nuclear effect distribution function of the sea and valence quarks RvA(x2) RsA(X2) according to the two experimental data of the high energy /-h deep inelastic scattering process and high energy h-A Drell-Yan process by using a consistent mathematical treatment of the iterative method. Under the nonconstant K circumstance, and on the basis of the above two experimental data, we calculate the sea and valence quark distributions affected by nuclear effect for C, Ca, Fe respectively. Some scientifically information of nuclear effect for different quarks has been preliminarily obtained from both experiments. We provide the relevant data results. Finally we estimate as well the influence on nuclear structure function after considering QCD non-perturbation effect and the energy lose in the nuclear Drell-Yan process by improving related original treatments.