Z. J. He

Elliptic flow of phi mesons and strange quark collectivity

Based on a multiphase transport model, we have studied the elliptic flow v{sub 2} of {phi} mesons from the reconstructed K{sup +}K{sup -} decay channel at the top Relativistic Heavy Ion Collider energy at Brookhaven National Laboratory. The dependences of v{sub 2} on transverse momentum p{sub T} and collision centrality are presented and the rescattering effect of {phi} mesons in the hadronic phase is also investigated. The results show that experimental measurement of v{sub 2} for {phi} mesons can retain the early collision information before the {phi} decays and that the {phi} v{sub 2} value obeys the constituent quark number scaling that has been observed for other mesons and baryons. Our study indicates that the {phi} v{sub 2} mostly reflects partonic-level collectivity developed during the early stage of the nucleus-nucleus collision and the strange and light up/down quarks have developed similar angular anistropy properties at the hadronization.

Di-hadron azimuthal correlation and Mach-like cone structure in a parton/hadron transport model

Abstract In the framework of a multi-phase transport model (AMPT) with both partonic and hadronic interactions, azimuthal correlations between trigger particles and associated scattering particles have been studied by the mixing-event technique. The momentum ranges of these particles are 3 p T trig 6 GeV / c and 0.15 p T assoc 3 GeV / c (soft), or 2.5 p T trig 4 GeV / c and 1 p T assoc 2.5 GeV / c (hard) in Au + Au collisions at s N N = 200 GeV . A Mach-like structure has been observed in correlation functions for central collisions. By comparing scenarios with and without parton cascade and hadronic rescattering, we show that both partonic and hadronic dynamical mechanisms contribute to the Mach-like structure of the associated particle azimuthal correlations. The contribution of hadronic dynamical process cannot be ignored in the emergence of Mach-like correlations of the soft scattered associated hadrons. However, hadronic rescattering alone cannot reproduce experimental amplitude of Mach-like cone on away-side, and the parton cascade process is essential to describe experimental amplitude of Mach-like cone on away-side. In addition, both the associated multiplicity and the sum of p T decrease, while the 〈 p T 〉 increases, with the impact parameter in the AMPT model including partonic dynamics from string melting scenario.

Intermediate mass dileptons from a chemically non-equilibrated quark-gluon plasma

We have studied the evolution and dilepton production of a chemically equilibrating quark-gluon plasma considering finite baryon density based on Juttner distribution of partons, and found that due to the increasing of the quark phase life-time with increasing initial quark chemical potential, high initial temperature, large gluon density of the system as well as large gluon fusion gg --> c (c) over bar cross section in the intermediate mass region, quark-antiquark annihilation q (q) over bar --> l (l) over bar, especially, thermal charmed quarks from the gluon fusion gg --> c (c) over bar and quark-antiquark annihilation q (q) over bar --> c (c) over bar provide a dominant contribution to dileptons, resulting in a significant enhancement of intermediate mass dileptons

Enhancement of intermediate mass dileptons from expanding hot quark-gluon matter

Abstract A study of the production of intermediate mass dileptons from the quark phase and hadronic interactions as well as non-thermal contributions (Drell–Yan pairs, charmed hadronic decays) in the initial stage has been carried out based on a relativistic hydrodynamic model describing the evolution of a quark–gluon matter fire-cylinder. We find that due to the influence of the phase boundary on the evolution of the quark–gluon matter system and the high initial temperature of the quark–gluon matter produced at RHIC energies, the contribution of the quark phase to dileptons is obviously enhanced and is more important than those from hadronic interactions and even is comparable with those from non-thermal contributions. It is shown that the enhancement of intermediate mass dileptons is a possible signature for the quark–gluon matter formation in heavy ion collisions at RHIC energies.

Azimuthal correlations of hadrons in a partonic/hadronic transport model

By using a multi‐phase transport (AMPT) model with both partonic and hadronic interactions, di‐hadron and three‐particle azimuthal correlations between trigger particles and associated scattering particles in Au + Au collisions at sNN = 200 GeV have been studied by the mixing‐event technique. A Mach‐like structure has been observed in the di‐hadron and three‐particle correlation functions in central collisions. By comparing the scenarios with and without parton cascade and/or hadronic rescattering, it is shown that both partonic and hadronic dynamical mechanisms contribute to the Mach‐like structure of the scattered particle azimuthal correlations. However, only hadronic rescattering is unable to reproduce experimental amplitude of Mach‐like cone on away‐side, instead the parton cascade process is essential to describe experimental amplitude of Mach‐like cone on away‐side.