High energy scattering and emission in QED&QCD media

Xabier Feal

Published 2018-12-17Version 1

A formalism for the evaluation of the intensity of photon and gluon bremsstrahlung in QED and QCD condensed media is presented which considers general interactions beyond the Fokker-Planck/Gaussian approximation, the angular distribution of the final particles and admits finite or structured target calculations. The Boltzmann/transport approaches of Migdal, Bell and the Baier-Dokshitzer-Mueller-Peign\'e-Schiff group, and the light-cone path integral formalisms of Zakharov and Wiedemann and Gyulassy are recovered as particular cases within the Fokker-Planck limit, which assumes Brownian motion for the intervening particles. Weinberg's soft photon theorem is shown to saturate the Landau-Pomeranchuk-Migdal supression in the soft photon/gluon regime of vanishing phases. The intensity under realistic screened interactions is larger than the existing Fokker-Planck results by a factor 3-4 and the changes can not be accounted for by a single definition of the medium transport properties through $\hat{q}$. This may also suggest that larger gluon elastic cross sections, leading to the hypothesis of strongly coupled Quark Gluon Plasma, may not be required to match the data.