Cosmological and astrophysical probes of dark baryons

TL;DR

This paper investigates the cosmological and astrophysical effects of a hypothetical dark baryon that mixes with neutrons, deriving constraints from early universe observations and neutron star data, and explores its potential as dark matter.

Contribution

It introduces new limits on dark baryon properties based on cosmological and astrophysical observations, and identifies viable parameter space for dark baryons as dark matter candidates.

Findings

Strong constraints from nucleosynthesis and CMB on dark baryon-neutron mixing

Neutron star temperature measurements limit dark baryon decay

Viable dark matter parameter space identified for dark baryons

Abstract

We examine the cosmological and astrophysical signatures of a "dark baryon," a neutral fermion that mixes with the neutron. As the mixing is through a higher-dimensional operator at the quark level, production of the dark baryon at high energies is enhanced so that its abundance in the early universe may be significant. Treating its initial abundance as a free parameter, we derive new, powerful limits on the properties of the dark baryon. Primordial nucleosynthesis and the cosmic microwave background provide strong constraints due to the inter-conversion of neutrons to dark baryons through their induced transition dipole, and due to late decays of the dark baryon. Additionally, neutrons in a neutron star could decay slowly to dark baryons, providing a novel source of heat that is constrained by measurements of pulsar temperatures. Taking all the constraints into account, we identify parameter space where the dark baryon can be a viable dark matter candidate and discuss promising avenues for probing it.