Transverse spectrum of bremsstrahlung in finite condensed media

TL;DR

This paper develops a formalism to evaluate bremsstrahlung photon emission from high-energy electrons in finite media, accounting for suppression effects and medium coherence, with predictions matching SLAC data.

Contribution

It introduces a comprehensive formalism for photon radiation in finite condensed media, including suppression effects and medium coherence, with detailed comparisons between different interaction models.

Findings

Landau-Pomeranchuk-Migdal suppression saturates at a characteristic photon energy.

Medium coherence effects lead to dielectric suppression and transition radiation.

Predictions agree well with experimental data from SLAC.

Abstract

A formalism is presented in which the radiation of photons off high energy electrons during a multiple scattering process with finite condensed media can be evaluated for a general interaction. We show that the arising Landau-Pomeranchuk-Migdal suppression for finite size targets saturates at some characteristic photon energy. Medium coherence effects in the photon dispersion relation can be also considered leading to a dielectric suppression or transition radiation effects in the soft part of the spectrum. The main results of our formulation are presented for a Debye screened interaction and its well-known Fokker-Planck approximation, showing that for finite size targets or for the angular distributions of the final particles the differences between both scenarios cannot be reconciled into a single redefinition of the medium transport parameter $(\hat{q})$. Our predictions are in very good agreement with the experimental data collected at SLAC.