Jet Quenching Effects Of High Energy Nucleus-Nucleus Collisions In RHIC

Hard process are considered as a good tool to study the properties of the quark matter produced in ultra-relativistic heavy-ion collision because it can probe the early stage of the evolution of dense system, during which a quark-gluon plasma (QGP) could exist for a short period of time. One important aspect of hard processes is jet's energy loss or jet quenching due to gluon radiation induced by multiple rescattering for a energetic parton jet going through the strong interacting medium.In addition to the gluon radiation, the bremsstrahl ung processes induced by multiple rescattering include also the photon radiation. Based on the GW model, we apply the opacity expansion technique to investigate the induced photon radiation and dilepton production in strong interacting medium. The real photon radiation and the dilepton invariant-mass spectrums are given up to the first order in opacity expansion. It is shown that, both the real photon radiation and dilepton invariant spectrums decrease with increasing the transverse momentum: In the low transverse momentum region the rescattering effect plays an important role; At fixed transverse momentum the dilepton production induced by multiple rescattering decrease with increasing dilepton's invariant-mass. For real photon radiation the Abelian LPM effect lead to that the parton jet's energy loss haslinear dependence on the thickness of the targets instead of quadratic dependence arising from non-Abelian LPM effect for gluon radiation.Because parton jet energy loss gives rise to modification of fragmentation functions, jet quenching in heavy ion collision leads to the suppression of large transverse momentum hadrons spectra as compared to pp collision at the same energy. Taking into account the jet quenching, we calculate numerically single hadron spectra at next-to-leading order (NLO) and the ellipse flow parameter v2 caused by the asymmetric energy loss in transverse plane in Au+Au collisions (s^1/2=200GeV). It turns out that the jet quenching can describe the large pr pion and charged hadron spectra in heavy-ion collisions at the RHIC energies very well by different centrality in Au+Au. We also calculate dihadron production in Au+Au collisions (s^1/2=200GeV) and the corresponding parameter v2. It turns out that the invariable mass spectrum and large transverse momentum dihadron are all suppressed for the central nucleus-nucleus collision because of jet quenching effect. It is similar to the p-p collision, the produced hadron back-to-back correlation is strong for the peripheral nucleus-nucleus collision. This correlation is much weaker with decreasing the compact parameter. For central collision, the back-to-back correlation disappears. We show that w2 is approximately a constant in large transverse momentum region both in single hadron and dihadron production.