Azimuthal anisotropy of direct photons

TL;DR

This paper investigates the azimuthal anisotropy of direct photons resulting from electromagnetic bremsstrahlung in high-energy collisions, linking it to dipole cross section orientation and its impact on various collision processes.

Contribution

It introduces a theoretical framework connecting photon azimuthal anisotropy to dipole orientation dependence in the light-cone dipole model.

Findings

Azimuthal asymmetry in photon production is related to dipole cross section orientation.

The effect influences direct photon asymmetry in pA, AA collisions, DIS, and dilepton production.

Provides a theoretical basis for understanding photon anisotropy in high-energy collisions.

Abstract

The electromagnetic bremsstrahlung produced by a quark interacting with nucleons or nuclei is azimuthally asymmetric. In the light-cone dipole approach this effect is related to the orientation dependent dipole cross section. Such a radiation anisotropy is expected to contribute to the azimuthal asymmetry of direct photons in pA and AA collisions, as well as in DIS and in the production of dileptons.