High energy scattering and emission in QED&QCD media

TL;DR

This paper develops a comprehensive formalism for photon and gluon bremsstrahlung in QED and QCD media, extending beyond traditional approximations and revealing larger emission intensities that challenge existing models and assumptions about the medium.

Contribution

It introduces a generalized formalism for radiation in QED/QCD media that includes complex interactions and structured targets, unifying various existing approaches as special cases.

Findings

Realistic interactions increase emission intensity by 3-4 times compared to Fokker-Planck models.

The formalism shows that larger elastic cross sections may not be necessary to explain experimental data.

Weinberg's theorem explains the suppression saturation in soft photon/gluon emission.

Abstract

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.