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Dark Matter interpretation of the neutron decay anomaly

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