Annihilation signatures of neutron dark decay models in neutron oscillation and proton decay searches

Abstract: We point out that two models that reconcile the neutron lifetime anomaly via dark decays of the neutron, also predict dark matter-neutron ($\bar{\chi}-n$) annihilation that may be observable in neutron-antineutron oscillation and proton decay searches at Super-Kamiokande, Hyper-Kamiokande and DUNE. We study signatures of $\bar{\chi}n\to \gamma\pi<sup>0$ (or multi-$\pi<sup>0$) and $\bar{\chi}n\to \phi\gamma\pi<sup>0$ (or $\phi+$multi-$\pi<sup>0$), where $\phi$ is an almost massless boson in one of the two models.