Virtual Photon Emission from Quark-Gluon Plasma

Abstract

We recently proposed an empirical approach for the Landau-Pomeranchuk-Migdal (LPM) effects in photon emission from the quark gluon plasma as a function of photon mass. This approach was based on Generalized Emission Functions (GEF) for photon emission, derived at a fixed temperature and strong coupling constant. In the present work, we have extended the LPM calculations for several temperatures and strong coupling strengths. The integral equations for (${\bf \tilde{f}(\tilde{p}_\perp)}$) and ($\tilde{g}({\bf \tilde{p}_\perp})$) are solved by the iterations method for the variable set \{$p_0,q_0,Q^2,T,\alpha_s$\}, considering bremsstrahlung and $\bf aws$ processes. We generalize the dynamical scaling variables, $x_T$, $x_L$, for bremsstrahlung and {\bf aws} processes which are now functions of variables $p_0,q_0,Q^2,T,\alpha_s$. The GEF introduced earlier, $g^b_T$, $g^a_T$, $g^b_L$, $g^a_L$, 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 can be calculated as a one dimensional integral over these GEF and parton distribution functions in the plasma. However, for phenomenological studies of experimental data, one needs a simple empirical formula without involving parton momentum integrations. Therefore, we present a phenomenological formula for imaginary photon polarization tensor as a function of \{$q_0,Q^2,T,\alpha_s$\} that includes bremsstrahlung and $\bf aws$ mechanisms along with LPM effects.