Dark Matter interpretation of the neutron decay anomaly

Abstract

We add to the Standard Model a new fermion $\chi$ with minimal baryon number 1/3. Neutron decay $n\to \chi \chi \chi$ into non-relativistic $\chi$ can account for the neutron decay anomaly, compatibly with bounds from neutron stars. $\chi$ can be Dark Matter, and its cosmological abundance can be generated by freeze-in dominated at $T\sim m_n$. The associated processes $n\to \chi \chi \chi \gamma$, hydrogen decay $\mathrm{H}\to \chi \chi \chi \nu (\gamma )$ and DM-induced neutron disappearance $\bar{\chi }n\to \chi \chi (\gamma )$ have rates below experimental bounds and can be of interest for future experiments.

Comments: 15 pages, 3 figures. Published version. Associated webinar: https://youtu.be/Q1bUrpQqTQs