Baryonic Axion in neutron-antineutron oscillation

TL;DR

This paper explores how axions, as dark matter candidates, could influence neutron-antineutron oscillations, revealing a Rabi resonance effect and constraining QCD axion models based on their Goldstone nature.

Contribution

It introduces a framework for analyzing axion couplings to neutron-antineutron oscillations, highlighting a resonance phenomenon and providing new constraints on QCD axion scenarios.

Findings

Rabi resonance occurs in neutron-antineutron oscillations due to axion couplings.

Most QCD axion models are excluded based on their Goldstone nature.

Unconstrained effects are identified for Axion Like Particles (ALPs).

Abstract

The accidental baryonic symmetry is expected to be broken and required from the observed matter-antimatter asymmetry. The neutron-antineutron oscillating system is the hallmark of $\Delta \mathcal{B} = 2$ models which have the benefits of not inducing proton decay. We study this system in a framework allowing the most general couplings to understand how a dark matter candidate such as the axion may couple to the oscillation. In particular a Rabi resonance phenomenon occurs, and this effect is unconstrained for Axion Like Particles (ALPs) models. Regarding the QCD axion, its Goldstone nature leads to a robust exclusion of the majority of scenarios allowed.