J. L. Long

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.

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

Viscosity and dilepton production of a chemically equilibrating quark-gluon plasma at finite baryon density

By considering the effect of shear viscosity we have investigated the evolution of a chemically equilibrating quark-gluon plasma at finite baryon density. Based on the evolution of the system we have performed a complete calculation for the dilepton production from the following processes: qq -> l1q, qq -> gll, Compton-like scattering (qg -> qll,qg -> qll), gluon fusion (gg -> cc), annihilation (qq -> cc), as well as the multiple scattering of quarks. We have found that quark-antiquark annihilation, Compton-like scatterring, gluon fusion, and multiple scattering of quarks give important contributions. Moreover, we have also found that the dilepton yield is an increasing function of the initial quark chemical potential, and the increase of the quark phase lifetime because of the viscosity also obviously raises the dilepton yield.

Δ-scaling and heat capacity in relativistic ion collisions

The Δ-scaling method has been applied to the total multiplicity distribution of the relativistic ion collisions of p+p, C+C and Pb+Pb which were simulated by a Monte Carlo package, LUCIAE 3.0. It is found that the Δ-scaling parameter decreases with increasing system size. Moreover, the heat capacities of different mesons and baryons have been extracted from the event-by-event temperature fluctuation in the region of low transverse mass and they shows the dropping trend with increasing impact parameter.

The shear viscosity of a chemically equilibrating quark-gluon plasma at finite baryon density

Taking account of elastic gg -> gg and bremsstrahlung gg -> ggg processes, as well as quark elastic scattering, we calculated the shear viscous coefficient of a chemically equilibrating quark-gluon plasma at finite baryon density. We found that the inelastic bremsstrahlung processes make the shear viscosity remarkably lower, and the ratio of shear viscosity to entropy density./s increases with increasing initial quark chemical potential. Considering the effect of shear viscosity the evolution of the QGP system was investigated. We found that the evolution of the system becomes slower owing to viscosity compared to the one in the ideal case, and the inelastic bremsstrahlung processes make the slower rate of the system not as much as in our previous calculations. Copyright (C) EPLA, 2013

Evolution and photons of a chemically equilibrating quark-gluon plasma at finite baryon density

We study the evolution of a chemically equilibrating quark–gluon plasma in a (3+1)-dimensional spacetime at finite baryon density and its photon production. We find that the photon production is a strongly decreasing function of the ratio of quark chemical potential to temperature.

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.