skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Generalized emission functions for photon emission from quark-gluon plasma

Abstract

The Landau-Pomeranchuk-Migdal effects on photon emission from the quark-gluon plasma have been studied as a function of photon mass, at a fixed temperature of the plasma. The integral equations for the transverse vector function [f-tilde)(p-tilde){sub (perpendicular)})] and the longitudinal function [g-tilde)(p-tilde){sub (perpendicular)})] consisting of multiple scattering effects are solved by the self-consistent iterations method and also by the variational method for the variable set {l_brace}p{sub 0},q{sub 0},Q{sup 2}{r_brace}. We considered the bremsstrahlung and the off shell annihilation (aws) processes. We define two new dynamical scaling variables, x{sub T},x{sub L}, for bremsstrahlung and aws processes which are functions of variables p{sub 0},q{sub 0},Q{sup 2}. We define four new emission functions for massive photon emission represented by g{sub T}{sup b},g{sub T}{sup a},g{sub L}{sup b},g{sub L}{sup a} and we constructed these using the exact numerical solutions of the integral equations. These four emission functions have been parametrized by suitable simple empirical fits. Using the empirical emission functions, we calculated the imaginary part of the photon polarization tensor as a function of photon mass and energy.

Authors:
 [1]
  1. Nuclear Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)
Publication Date:
OSTI Identifier:
20990995
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 2; Other Information: DOI: 10.1103/PhysRevC.75.021902; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ANNIHILATION; BREMSSTRAHLUNG; FUNCTIONS; INTEGRAL EQUATIONS; MASS; MULTIPLE SCATTERING; NUMERICAL SOLUTION; PHOTON EMISSION; PHOTONS; PLASMA; QUARK MATTER; VECTORS

Citation Formats

Suryanarayana, S. V. Generalized emission functions for photon emission from quark-gluon plasma. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.021902.
Suryanarayana, S. V. Generalized emission functions for photon emission from quark-gluon plasma. United States. doi:10.1103/PHYSREVC.75.021902.
Suryanarayana, S. V. Thu . "Generalized emission functions for photon emission from quark-gluon plasma". United States. doi:10.1103/PHYSREVC.75.021902.
@article{osti_20990995,
title = {Generalized emission functions for photon emission from quark-gluon plasma},
author = {Suryanarayana, S. V.},
abstractNote = {The Landau-Pomeranchuk-Migdal effects on photon emission from the quark-gluon plasma have been studied as a function of photon mass, at a fixed temperature of the plasma. The integral equations for the transverse vector function [f-tilde)(p-tilde){sub (perpendicular)})] and the longitudinal function [g-tilde)(p-tilde){sub (perpendicular)})] consisting of multiple scattering effects are solved by the self-consistent iterations method and also by the variational method for the variable set {l_brace}p{sub 0},q{sub 0},Q{sup 2}{r_brace}. We considered the bremsstrahlung and the off shell annihilation (aws) processes. We define two new dynamical scaling variables, x{sub T},x{sub L}, for bremsstrahlung and aws processes which are functions of variables p{sub 0},q{sub 0},Q{sup 2}. We define four new emission functions for massive photon emission represented by g{sub T}{sup b},g{sub T}{sup a},g{sub L}{sup b},g{sub L}{sup a} and we constructed these using the exact numerical solutions of the integral equations. These four emission functions have been parametrized by suitable simple empirical fits. Using the empirical emission functions, we calculated the imaginary part of the photon polarization tensor as a function of photon mass and energy.},
doi = {10.1103/PHYSREVC.75.021902},
journal = {Physical Review. C, Nuclear Physics},
number = 2,
volume = 75,
place = {United States},
year = {Thu Feb 15 00:00:00 EST 2007},
month = {Thu Feb 15 00:00:00 EST 2007}
}
  • The emission rates for photons and dileptons from a quark-gluon plasma are related to the thermal expectation value of an electromagnetic current-current correlation function. This correlation function possesses an invariant-tensor decomposition with structure functions entirely analogous to W/sub 1/ and W/sub 2/ of deep-inelastic scattering of leptons from hadronic targets. The thermal scaling properties of the appropriate structure functions for thermal emission are derived. The thermal structure functions may be computed in a weak-coupling expansion at high plasma temperature. The rates for thermal emission are estimated, and for dileptons, using conservative estimates of the plasma temperature, the thermal-emission process ismore » argued to dominate over the Drell-Yan process for dilepton masses 600 MeV« less
  • We present phenomenological formulas for virtual photon emission rates from a thermalized quark-gluon plasma (QGP) that include bremsstrahlung and annihilation with scattering (AWS) mechanisms along with the Landau-Pomeranchuk-Migdal (LPM) effects. For this purpose we follow the approach of generalized emission functions (GEF) for virtual photon emission, we showed earlier for a fixed temperature and strong coupling constant. In the present work, we extend the LPM calculations for several temperatures and strong coupling strengths, photon energies (q{sub 0}), photon mass (Q{sup 2}), and quark energies (p{sub 0}). We generalize the dynamical scaling variables, x{sub T},x{sub L}, for bremsstrahlung and AWS processesmore » that are now functions of variables p{sub 0},q{sub 0},Q{sup 2},T,{alpha}{sub s}. The GEF introduced earlier, g{sub T}{sup b},g{sub T}{sup a},g{sub L}{sup b},g{sub L}{sup a}, are also generalized for any temperatures and coupling strengths. From this, the imaginary part of the photon polarization tensor as a function of photon mass and energy has been calculated as a one-dimensional integral over these GEF and parton distribution functions in the plasma. By fitting these polarization tensors obtained from GEF method, we obtained a phenomenological formula for virtual photon emission rates as a function of (q{sub 0},Q{sup 2},T,{alpha}{sub s}) that includes bremsstrahlung and AWS mechanisms with LPM effects.« less
  • Cited by 25
  • In-medium interactions of a particle in a hot plasma are considered in the framework of thermal field theory. The formalism to calculate gauge-invariant rates for photon and dilepton production from the medium is given. In the application to a QED plasma, astrophysical consequences are pointed out. The photon production rate from strongly interacting quarks in the quark-gluon plasma, which might be formed in ultrarelativistic heavy ion collisions, is calculated in the previously unaccessible regime of photon energies of the order of the plasma temperature. For temperatures below the chiral phase transition, an effective field theory incorporating dynamical chiral symmetry breakingmore » is employed, and perturbative QCD at higher temperatures. A smooth transition between both regions is obtained. The relevance to the soft photon problem and to high energy heavy ion experiments is discussed. {copyright} {ital 1996 The American Physical Society.}« less
  • Two-photon intensity interferometry is used to probe the dynamics of quarks and gluons in a high-energy nucleus-nucleus collision. A (1+1)-dimensional expansion of the plasma according to Bjorken hydrodynamics as well as a (3+1)-dimensional expansion, both with a first-order phase transition, are considered. The correlation of high transverse-momentum photons is sensitive to the details of the space-time evolution of the high density QCD plasma. The so-called longitudinal'' and outward'' correlations are found to be dramatically affected by the transverse expansion of the system.