Dark Matter interpretation of the neutron decay anomaly

Abstract

We add to the Standard Model a new fermion χ with minimal baryon number 1/3. Neutron decay n → 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 ∼ mn. The associated processes n → χχχγ, hydrogen decay H → χχχν(γ) and DM-induced neutron disappearance χ¯ n → χχ(γ) have rates below experimental bounds and can be of interest for future experiments.