Photon bremsstrahlung from quark jet via transverse and longitudinal scatterings: single versus multiple scatterings

TL;DR

This paper investigates jet-bremsstrahlung photon production in dense nuclear matter, analyzing effects of single versus multiple scatterings, including transverse and longitudinal momentum exchanges, within a deep-inelastic scattering framework.

Contribution

It derives the photon bremsstrahlung spectrum considering both transverse broadening and longitudinal drag/diffusion, and compares single and multiple scattering effects, highlighting the coupling contributions.

Findings

Coupling between scatterings adds to photon radiation.

Drag and diffusion effects dominate at small momentum exchange.

Multiple scatterings can enhance medium-induced photon emission.

Abstract

We study the production of jet-bremsstrahlung photons through the scattering with the constituents of a dense nuclear matter within the framework of deep-inelastic scattering off a large nucleus. Applying a gradient expansion up to the second order for the exchanged three-dimensional momentum between jet and medium, we derive the single photon bremsstrahlung spectrum with the inclusion of the contributions from the transverse broadening as well as the longitudinal drag and diffusion of the hard parton's momentum. We also compare the medium-induced photon radiation spectra for single scattering and from the resummation of multiple scatterings. It is found that the coupling between different scatterings can give additional contribution to medium-induced photon radiation, while for small momentum exchange, the leading contribution from the drag and diffusions to the photon emission spectra remain the same for single and multiple scatterings.