Cornering the axion with CP-violating interactions
Abstract
Besides CP-preserving interactions, axions and axion-like particles may also have small CP-violating scalar Yukawa interactions with nucleons and electrons. Any such interaction will generate macroscopic monopole-dipole forces which can be searched for experimentally. When the best experimental limits on scalar interactions are combined with stellar energy-loss arguments constraining pseudoscalar interactions, strong bounds can be set on CP-violating axion couplings which almost intersect the expectation for QCD models. Over the years, both astrophysical and laboratory tests have improved. We provide a much-needed up-to-date compilation of these constraints, showing improvements in some regions of parameter space by factors between 40 and 130. We advocate experimental opportunities, without astrophysical or dark-matter assumptions, to track down the axion in the lesser-explored corners of its parameter space.
Cite
@article{arxiv.2010.03889,
title = {Cornering the axion with CP-violating interactions},
author = {Ciaran A. J. O'Hare and Edoardo Vitagliano},
journal= {arXiv preprint arXiv:2010.03889},
year = {2021}
}
Comments
17 pages, 4 figures. Matches published version. Some text, corrections, and clarifications have been added between v2 and v3. Code and txt files for all limits can be found at https://github.com/cajohare/AxionLimits