Pre-equilibrium dilepton production from an anisotropic quark-gluon plasma

Journal Article · Mon Sep 15 04:00:00 EDT 2008 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PHYSREVC.78.034917· OSTI ID:21192232

Martinez, Mauricio ^[1]; Strickland, Michael ^[2]

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1. Helmholtz Research School, Otto Stern School, Johann Wolfgang Goethe-Universitaet Frankfurt, Ruth-Moufang-Strasse 1, D-60438 Frankfurt am Main (Germany)
2. Institute fuer Theoretische Physik and Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-Universitaet Frankfurt, Max-von-Laue-Strasse 1, D-60438 Frankfurt am Main (Germany)

We calculate leading-order dilepton yields from a quark-gluon plasma that has a time-dependent anisotropy in momentum space. Such anisotropies can arise during the earliest stages of quark-gluon plasma evolution due to the rapid longitudinal expansion of the created matter. Two phenomenological models for the proper-time dependence of the parton hard momentum scale, p{sub hard}, and the plasma anisotropy parameter, {xi}, are constructed that describe the transition of the plasma from its initial nonequilibrium state to an isotropic thermalized state. The first model constructed interpolates between 1+1 dimensional free streaming at early times and 1+1 dimensional ideal hydrodynamical expansion at late times. In the second model we include the effect of collisional broadening of the parton distribution functions in the early-time pre-equilibrium stage of plasma evolution. We find for both cases that for fixed initial conditions high-energy dilepton production is enhanced by pre-equilibrium emission. When the models are constrained to fixed final pion multiplicity the dependence of the resulting spectra on the assumed plasma isotropization time is reduced. Using our most realistic collisionally broadened model we find that high-transverse-momentum dilepton production would be enhanced by at most 40% at the Relativistic Heavy Ion Collider and 50% at the CERN Large Hadron Collider if one assumes an isotropization/thermalization time of 2 fm/c. Given sufficiently precise experimental data this enhancement could be used to determine the plasma isotropization time experimentally.

• OSTI ID: 21192232
• Journal Information: Physical Review. C, Nuclear Physics, Journal Name: Physical Review. C, Nuclear Physics Journal Issue: 3 Vol. 78; ISSN 0556-2813; ISSN PRVCAN
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ANISOTROPY
BROOKHAVEN RHIC
CERN
CERN LHC
DISTRIBUTION FUNCTIONS
EMISSION
EQUILIBRIUM
LEPTONS
MULTIPLICITY
ONE-DIMENSIONAL CALCULATIONS
PARTICLE PRODUCTION
PIONS
PLASMA
QUARK MATTER
SIMULATION
SPECTRA
THERMALIZATION
TIME DEPENDENCE
TRANSVERSE MOMENTUM