X_cJ Suppression Induced By Nucleons In High Energy Nucleus-Nucleus Collisions

One of the most important characteristics of high energy nucleus-nucleus collisions is the large amount of energy involved . When a large fraction of this energy is deposited in a small region of space in a short duration of time, the energy density can be very high. An energy density of the order of a few GeV/fm2 may be achieved. This energy density of nuclear matter in equilibrium, may favor the formation of new forms of matter such as the quark-gluon plasma (QGP).The search for new forms of matter under extreme conditions of high energy densities and high temperatures is an important objective of high energy heavy-ion collisions.The produced matter in nucleus-nucleus collisions may make an excursion from the hadron phase into the QGP phase. Subsequent cooling allows the matter to return to the hadron phase and to appear as hadrons. During the time when the matter is in the QGP phase, particles which arise from the interaction between the constituents of the plasma will provide information concerning the state of the plasma. The detection of the products of their interactions will be useful as a plasma diagnostic tool.As one of the signatures for the QGP, J/ production and suppression in high energy nucleus-nucleus collisions have been studied for more than two decades. Since J/ serves a special role of the "border guard" on the mysterious border of perturbative world of quarks and gluons and non-perturbative world of hadrons, the production of J/ and some other properties can be described in perturbative theory, but its further interaction with surrounding matter is essentially soft in nature and can not be treated perturbatively. The dissociationcross sections used in this thesis are obtained in the frame work of an essentially non-perturbative approach based on a hadronic model that incorporates quark confinement.The nucleus-nucleus collisions at RHIC or LHC energies have been divided into four stages: (1)initial parton-parton scattering: (2)prethermal parton matter: (3)thermalized parton plasma: (4)hadronic matter: In order to clearly realize the suppression in the deconfined phase, the J/ suppression in hadronic matter has to be separated out. Meanwhile the experimentally observed results is the prompt J/ production, including the direct J/ production, the decay of 'and the radiative feeddown of XcJ- The main content of this thesis is to calculate xcJ suppression in the hadronic matter at CERN-SPS and RHIC energies.Firstly we consider an important factor which will affect the results of XcJ suppression: the thermal average of the XcJ dissociation cross sections multiplied by the relative velocity of XcJ and nucleon(antinucleon), while XcJ moves in hadronic matter produced in high energy nucleus-nucleus collisions. The quantity can be regarded as the mean capability of protons to dissolve a XcJ which is moving through a thermal proton gas. Nucleon-Xcj dissociation cross sections obtained in the quark-exchange mechanism are applied to study XcJ suppression in hadronic matter created in central Pb+Pb and S+Pb collisions at CERN-SPS energies. The survival probabilities of XcJ show that the collisions with nucleons and antinucleons is appreciable.Another important work in the thesis is calculating XcJ suppression in hadronic matter produced in central Au+Au collisions at RHIC energies 130 GeV and 200 GeV. In calculation the nucleon and antinucleon distributions in hadronic matter are results of evolution from their freeze-out distributionswhich well fit the experimental transverse momentum spectra of proton and antiproton. We predict that XcJ mesons at low transverse momentum in the central rapidity region are almost dissociated by nucleons and antinucleons in hadronic matter. So this results predict a great contribution to the total J/ suppression.