Breakdown of the hard thermal loop expansion for quasi-real photons production

Abstract

We discuss the bremsstrahlung production of soft real and virtual photons in a quark-gluon plasma at thermal equilibrium beyond the Hard Thermal Loop (HTL) resummation. The physics is controlled by the ratio Q 2 /q 2 0 of the virtuality to the energy. When Q 2 /q 2 0 ≪ g 2 , where g is the strong coupling constant, the emission rate is enhanced by a factor 1/g 2 over the HTL results due to light-cone singularities and the bremsstrahlung is induced by scattering of the quark via both transverse and longitudinal soft gluon exchanges. When Q 2 /q 2 0 increases, the enhancement factor is given by q 2 0 /Q 2 . When this ratio is near unity, the bremsstrahlung contribution is of the same order as the rate predicted by the HTL resummation. In that case, the bremsstrahlung is induced by both soft and hard gluon exchanges.

Remarks on transient effects for photon production in heavy ion collisions

“…for which n γ (ω) = 0. In this case, the photon population 7 When ρ(t i ) = exp(−H/T ), there is an explicit dependence of the initial density matrix on the coupling constant e. It is known that this dependence is taken care of without changing any formula, simply by appending a vertical branch to the time path [33], going from t i to t i −i/T . Moreover, it has been shown that the contribution of this vertical branch can be taken into account if one enforces the KMS condition at each intermediate step of the calculation [33,34,35].…”

“…These rates have been evaluated at 1-loop 1 in [3,4,5], at 2-loop in [6,7,8,9], and the Landau-Pomeranchuk-Migdal [10,11,12] corrections have been resummed in [13,14,15,16,17,18,19]. Up-to-date reviews of the situation regarding photon and dilepton production in equilibrium can be found in [20,21,22,23].…”

Theoretical Study of Photon Transition for Quark–Quark Interaction at Bremsstrahlung Process

“…The quarks interaction that occurs within the many quarks mater phases includes three important interaction (Compton scattering, annihilation and bremsstrahlung), these interactions occur at one time, But make a mental analysis in the study of these interactions, So that each separated by a phenomenon, when examined from the rest of the phenomena, Because of different a Mont of energy each interaction phenomenon for the rest of the phenomena, So one can understand the behavior of particles, According to the form of graphic curves in the search, we will prevail in this thesis to study the phenomenon of (bremsstrahlung) (Aurenche et al, 1997;Landau et al, 1953) in reaction (Quarkgluon).…”

γ-radiation of thermalized Quark-Gluon-Plasma

“…It worth mentioning that the underlying physical processes in the one loop diagram are the 2 ↔ 2 processes, Compton and annihilation. However, it was shown [ 4,5,6] that bremsstrahlung and the new process of annihilation of an off-shell quark (on the left of figure 1) contribute to leading order. These processes appear only at the two loop level in the effective theory.…”