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    Please use this identifier to cite or link to this item: http://tkuir.lib.tku.edu.tw:8080/dspace/handle/987654321/72744

    Title: Direct photons: A nonequilibrium signal of the expanding quark-gluon plasma
    Authors: Wang, S.Y.;Boyanovsky, D.;Ng, K.W.
    Contributors: 淡江大學物理學系
    Keywords: Direct photon production;Quark–gluon plasma;Relativistic heavy-ion collisions;Finite-temperature field theory
    Date: 2001-08
    Issue Date: 2011-10-24 11:05:36 (UTC+8)
    Abstract: Direct photon production from a longitudinally expanding quark–gluon plasma (QGP) at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies is studied with a real-time kinetic description that is consistently incorporated with hydrodynamics. Within Bjorken's hydrodynamical model, energy nonconserving (anti)quark bremsstrahlung q(q̄)→q(q̄)γ and quark–antiquark annihilation qq̄→γ are shown to be the dominant nonequilibrium effects during the transient lifetime of the QGP. For central collisions we find a significant excess of direct photons in the range of transverse momentum 1−2≲pT≲5 GeV/c as compared to equilibrium results. The photon rapidity distribution exhibits a central plateau. The transverse momentum distribution at midrapidity falls off with a power law p−νT with 2.5≲ν≲3 as a consequence of these energy nonconserving processes, providing a distinct experimental nonequilibrium signature. The power law exponent ν increases with the initial temperature of the QGP and hence with the total multiplicity rapidity distribution dNπ/dy.
    Relation: Nuclear Physics A 699, pp.819-846
    DOI: 10.1016/S0375-9474(01)01288-X
    Appears in Collections:[Graduate Institute & Department of Physics] Journal Article

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