Local strong parity violation and new possibilities in experimental study of non-perturbative QCD

TL;DR

This paper discusses the experimental investigation of local parity violation in quantum chromodynamics through the chiral magnetic effect, proposing new collision methods to distinguish signal from background in heavy-ion collisions.

Contribution

It introduces novel experimental approaches, including specific collision configurations, to better detect and understand the chiral magnetic effect and local parity violation in QCD.

Findings

STAR results are consistent with chiral magnetic effect expectations

Proposes using U+U collisions to separate effects from backgrounds

Suggests isobaric collisions for more quantitative analysis

Abstract

Quark interaction with topologically non-trivial gluonic fields, instantons and sphalerons, violates \P and \CP symmetry. In the strong magnetic field of a non-central nuclear collision such interactions lead to the charge separation along the magnetic field, the so called chiral magnetic effect, which manifests local parity violations. An experimental observation of the chiral magnetic effect would be a direct proof for the existence of such physics. Recent STAR results on charge and the reaction plane dependent correlations are consistent with theoretical expectations for the chiral magnetic effect. IIn this paper I discuss different approaches to experimental study of the local parity violation, and propose future measurements which can clarify the picture. In particular I propose to use central body-body U+U collisions to disentangle correlations due to chiral magnetic effect from possible background correlations due to elliptic flow. Further more quantitative studies can be performed with collision of isobaric beams.