Does chiral perturbation theory rule out QCD-based solutions to the strong CP problem?
High Energy Physics - Phenomenology
2019-05-15 v3 High Energy Physics - Theory
Nuclear Theory
Abstract
The conventional view is that a solution of the strong CP problem lies beyond QCD. A strong argument supporting this view is that the chiral expansion shows that observables depend on theta (unless a quark mass is zero); this eliminates the possibility that theta is physically irrelevant and appears to necessitate an explanation beyond the standard model. However, scenarios that solve the strong CP problem exist that are consistent with known chiral behavior; in these, QCD becomes nonviable as a theory for nonzero theta. Such scenarios appear to be compatible with lattice studies of the topological susceptibility.
Cite
@article{arxiv.1811.04833,
title = {Does chiral perturbation theory rule out QCD-based solutions to the strong CP problem?},
author = {Thomas D. Cohen},
journal= {arXiv preprint arXiv:1811.04833},
year = {2019}
}
Comments
The paper has been expanded. It now includes a discussion of how evidence for this class of scenario might be obtained