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 interconversion 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.
Bibliographical noteFunding Information:
We are indebted to David Morrissey for providing us with photon spectra from electromagnetic energy injection, and for fruitful conversations. The work of D. M. and N. R. is supported by the Natural Sciences and Engineering Research Council of Canada. triumf receives federal funding via a contribution agreement with the National Research Council Canada. M. P. is supported in part by U.S. Department of Energy Grant No. desc0011842.
© 2021 authors. Published by the American Physical Society.