The Energy Loss Effect On J/Ψ Production In Proton-Nuclear Collision

The relativistic collider facilities RHIC and LHC provide the opportunity to systematically study the physics of hot and ultradense matter in hadron-nucleus (pA) and nucleus-nucleus (AB) collisions at high energies. The systematic study of pA collisions at the same energies is essential to gain insight into the structure of the dense medium effects. Such effects, as the energy loss and shadowing, are absent or small in pp collisions, but become increasingly prominent in pA collisions, and are of major importance in AA reactions. By comparing pA and AA reactions involving very heavy nuclei, one may be able to distinguish basic hadronic effects that dominate the dynamics in pA collisions, from a quark-gluon formation predicted to occur in heavy ion AA collisions. To gain insight into the underlying hadronic processes, one has to study collisions that are expected to not lead to a QGP formation. Once the physics of"QCD at high densities"is better understood, the mechanisms of quark-gluon plasma formation and related collective phenomena in heavy ion collisions could be disentangled from the basic hadronic effects.Using the HKN parton distributions function of bound nucleon, we estimate the ratios of cross sections of J/ψproduction at 920GeV p-A collisions in a tungsten and carbon targets with Color Evaporate Model and two different energy loss models. The plots ofα( x F) vs. x F are presented at xF < 0. Furthermore, our results are compared with the experimental data of HERA-B. It follows that if only nucleus effect of the parton distributions function is taken into account, the results calculated is much different with experiment. So it is indicated that there must be other nuclear effects outside the effects of segmental distributed function on J/ψproduction in P-A collision. Comparing the results which are obtained only taking account of nucleus effect of parton distributions function with the data which is presented by using nucleus effect of parton distributions function and the GM energy loss, we find two conclusions are almost the same. It is showed that GM energy loss must be undervalued obviously. However, the energy loss in model of LQS energy loss with effect of segmental distributed function is overestimated, hence, the results is decided difference with the experimental data.