Testing dark decays of baryons in neutron stars

TL;DR

Observations of massive neutron stars challenge exotic dark decay models of neutrons, implying that any new physics must involve complex dark sectors to be consistent with astrophysical data.

Contribution

This paper shows that simple dark decay modes of neutrons cannot explain the neutron lifetime discrepancy without conflicting with neutron star mass observations.

Findings

Neutron stars over 1 solar mass exclude simple dark decay models.

Maximum neutron star mass in certain decay scenarios is 0.7 solar masses.

Complex dark sectors are required to reconcile neutron decay anomalies with astrophysical data.

Abstract

We demonstrate that the observation of neutron stars with masses greater than one solar mass places severe demands on any exotic neutron decay mode that could explain the discrepancy between beam and bottle measurements of the neutron lifetime. If the neutron can decay to a stable, feebly-interacting dark fermion, the maximum possible mass of a neutron star is 0.7 solar masses, while all well-measured neutron star masses exceed one solar mass. The survival of $2 M_\odot$ neutron stars therefore indicates that any explanation beyond the Standard Model for the neutron lifetime puzzle requires dark matter to be part of a multi-particle dark sector with highly constrained interactions.