Searching for missing direct photons in heavy-ion collisions with P and CP violation

TL;DR

This paper investigates how P- and CP-violating parameters affect synchrotron radiation in a plasma, potentially explaining the missing direct photons in heavy-ion collisions and deriving the chiral magnetic effect.

Contribution

It provides exact fermion wavefunctions in the presence of P- and CP-violation and applies these to quark-gluon plasma to address the missing direct photons puzzle.

Findings

P- and CP-violating parameters increase synchrotron radiation.

These parameters decrease the elliptic flow coefficient v2.

Results suggest a potential solution to the missing direct photons problem.

Abstract

We compute synchrotron radiation from a plasma in which $P$- and $CP$-violating parameters, a chiral chemical potential and a chiral gradient, couple to fermions. To do this, we compute exact wavefunctions for the fermions in the presence of these parameters and an external constant magnetic field. We find that these parameters increase the synchrotron radiation emitted by the fermions while also decreasing the traditionally large synchrotron radiation elliptic flow coefficient $v_2$. We apply these results to the quark-gluon plasma, where just such a contribution could provide a solution to the missing direct photons puzzle. We also use our wavefunctions to give a derivation of the chiral magnetic effect.