An effective QCD Lagrangian in the presence of an axial chemical potential

TL;DR

This paper explores how an axial chemical potential affects low-energy QCD meson physics, revealing parity violation and altered meson interactions, with potential implications for heavy ion collision experiments like RHIC.

Contribution

It introduces a modified linear sigma model to describe mesons under an axial chemical potential, highlighting parity breaking effects in QCD.

Findings

Axial charge induces parity violation in meson states.

Interactions forbidden by parity are modified or allowed.

Possible experimental signatures at RHIC are discussed.

Abstract

We consider the low energy realization of QCD in terms of mesons when an axial chemical potential is present; a situation that may be relevant in heavy ion collisions. We shall demonstrate that the presence of an axial charge has profound consequences on meson physics. The most notorious effect is the appearance of an explicit source of parity breaking. The eigenstates of strong interactions do not have a definite parity and interactions that would otherwise be forbidden compete with the familiar ones. In this work we focus on scalars and pseudoscalars that are described by a generalized linear sigma model. We comment briefly on the screening role of axial vectors in formation of effective axial charge and on the possible experimental relevance of our results, whose consequences may have been already seen at RHIC.