Polarization as a signature of local parity violation in hot QCD matter

TL;DR

This paper proposes a new method to detect local parity violation in hot QCD matter by measuring the helicity of final state baryons, revealing chirality imbalance without electromagnetic coupling.

Contribution

It introduces a novel approach to identify local parity violation through baryon helicity measurements, independent of the Chiral Magnetic Effect.

Findings

Helicity-helicity azimuthal correlation signals parity violation.

Chiral imbalance induces a polarization contribution proportional to axial chemical potential.

Method provides an alternative to electromagnetic coupling-based detection.

Abstract

We show that local parity violation due to chirality imbalance in relativistic nuclear collisions can be revealed by measuring the projection of the polarization vector onto the momentum, i.e. the helicity, of final state baryons. The proposed method does not require a coupling to the electromagnetic field, like in the Chiral Magnetic Effect. By using linear response theory, we show that, in the presence of a chiral imbalance, the spin 1/2 baryons and anti-baryons receive an additional contribution to the polarization along their momentum and proportional to the axial chemical potential. The additional, parity-breaking, contribution to helicity can be detected by studying helicity-helicity azimuthal angular correlation.