Transport rates and momentum isotropization of gluon matter in ultrarelativistic heavy-ion collisions

Journal Article · Wed Aug 15 04:00:00 EDT 2007 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PHYSREVC.76.024911· OSTI ID:21061985

Zhe, Xu; Greiner, Carsten ^[1]

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1. Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet Frankfurt, Max-von-Laue-Str. 1, D-60438 Frankfurt am Main (Germany)

To describe momentum isotropization of gluon matter produced in ultrarelativistic heavy-ion collisions, the transport rate of gluon drift and the transport collision rates of elastic (gg{r_reversible}gg) as well as inelastic (gg{r_reversible}ggg) perturbative quantum chromodynamics- (pQCD) scattering processes are introduced and calculated within the kinetic parton cascade Boltzmann approach of multiparton scatterings (BAMPS), which simulates the space-time evolution of partons. We define isotropization as the development of an anisotropic system as it reaches isotropy. The inverse of the introduced total transport rate gives the correct time scale of the momentum isotropization. The contributions of the various scattering processes to the momentum isotropization can be separated into the transport collision rates. In contrast to the transport cross section, the transport collision rate has an indirect but correctly implemented relationship with the collision-angle distribution. Based on the calculated transport collision rates from BAMPS for central Au+Au collisions at Relativistic Heavy Ion Collider energies, we show that pQCD gg{r_reversible}ggg bremsstrahlung processes isotropize the momentum five times more efficiently than elastic scatterings. The large efficiency of the bremsstrahlung stems mainly from its large momentum deflection. Due to kinematics, 2{yields}N (N>2) production processes allow more particles to become isotropic in momentum space and thus kinetically equilibrate more quickly than their back reactions or elastic scatterings. We also show that the relaxation time in the relaxation time approximation, which is often used, is strongly momentum dependent and thus cannot serve as a global quantity that describes kinetic equilibration.

• OSTI ID: 21061985
• Journal Information: Physical Review. C, Nuclear Physics, Journal Name: Physical Review. C, Nuclear Physics Journal Issue: 2 Vol. 76; ISSN 0556-2813; ISSN PRVCAN
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ANISOTROPY
APPROXIMATIONS
BREMSSTRAHLUNG
BROOKHAVEN RHIC
CROSS SECTIONS
DISTRIBUTION
ELASTIC SCATTERING
GLUON-GLUON INTERACTIONS
GLUONS
HEAVY ION REACTIONS
QUANTUM CHROMODYNAMICS
QUARK MATTER
QUARKS
RADIATION TRANSPORT
RELATIVISTIC RANGE
RELAXATION TIME
SPACE-TIME