Asymmetric Warm Dark Matter: from Cosmological Asymmetry to Chirality of Life

Abstract

We investigate a novel scenario involving asymmetric keV-range dark matter (DM) in the form of right-handed (sterile) neutrinos. Based on the Fermi-Dirac distribution, we demonstrate that asymmetric fermionic DM forms a Fermi degenerate gas, making it potentially colder than symmetric fermionic DM. This setup simultaneously accounts for the Universe's baryon asymmetry through tiny Yukawa interactions with Standard Model leptons and the Higgs field, and the homochirality of amino acids via decay into circularly polarized photons. This scenario can be investigated through soft X-ray searches conducted by current and upcoming space missions. The helical X-rays is a smoking-gun signal of our scenario. Additionally, we propose a new mechanism to suppress DM thermal production by introducing a light modulus, which may also benefit cosmology involving generic right-handed neutrinos with large mixing.