Spin Polarized Photons from Axially Charged Plasma at Weak Coupling: Complete Leading Order

TL;DR

This paper calculates the leading order P-odd photon emission rate from an axially charged QCD plasma at high temperature, revealing spin polarization effects as a signature of axial charge.

Contribution

It provides the first complete leading order calculation of the P-odd photon emission rate, including all relevant processes and resummations in weak coupling QCD.

Findings

Analytical expressions for P-odd emission rate derived.

Numerical evaluation of the rate presented.

Identification of P-odd photon polarization as a signature of axial charge.

Abstract

In the presence of (approximately conserved) axial charge in the QCD plasma at finite temperature, the emitted photons are spin-aligned, which is a unique P- and CP-odd signature of axial charge in the photon emission observables. We compute this "P-odd photon emission rate" in weak coupling regime at high temperature limit to complete leading order in the QCD coupling constant: the leading log as well as the constant under the log. As in the P-even total emission rate in the literature, the computation of P-odd emission rate at leading order consists of three parts: 1) Compton and Pair Annihilation processes with hard momentum exchange, 2) soft t- and u-channel contributions with Hard Thermal Loop re-summation, 3) Landau-Pomeranchuk-Migdal (LPM) re-summation of collinear Bremstrahlung and Pair Annihilation. We present analytical and numerical evaluations of these contributions to our P-odd photon emission rate observable.