Long-range axion forces and hadronic CP violation

TL;DR

This paper investigates long-range axion-mediated forces arising from CP violation, refining estimates of their coupling strengths from quark EDMs and Standard Model sources, with implications for dark matter and fundamental symmetries.

Contribution

It provides a detailed non-perturbative analysis of CP-odd axion forces and refines the estimates of their couplings from various CP-violating sources, including the Standard Model.

Findings

Refined estimates of axion-nucleon couplings from quark EDMs.

Analysis of Standard Model contributions to CP-odd axion interactions.

Implications for experimental searches of long-range axion forces.

Abstract

Axions and other pseudoscalar fields comprise an interesting class of ultralight dark matter candidates, that may independently play a role in solving the strong $CP$ problem. In the presence of $CP$-violating sources, these pseudoscalar fields can develop a coherent non-derivative coupling to nucleons, $\bar g_{aNN}$, thus mediating `mass-mass' and `mass-spin' forces in matter that can be probed experimentally. We revisit the non-perturbative generation of these $CP$-odd axion forces, and refine estimates of $\bar g_{aNN}$ generated by the EDMs and color EDMs of quarks. We also revisit the Standard Model contribution to $CP$-odd axion couplings generated by the phase of the Cabibbo-Kobayashi-Maskawa quark mixing matrix.