# 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.

## Key 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.

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Source: https://tomesphere.com/paper/1812.06903