Speaker
Description
We examine the sterile neutrino dark matter production in the primordial plasma with lepton asymmetry. The model parameter space (sterile-active neutrino mixing angle, sterile neutrino mass) is heavily limited by cosmological considerations and astrophysical observations. We argue that, with specifically tuned flavor fractions (electron, muon and tau) of the initial lepton asymmetry, one can mitigate limits from the Big Bang Nucleosynthesis on the model parameter space. This finding opens a window of lower sterile-active mixing angles. Likewise we show that, with lepton asymmetry disappearing from the plasma at certain intermediate stages of the sterile neutrino production, the spectrum of produced neutrinos becomes much colder, that weakens the limits on the model parameter space from observations of cosmic small-scale structures (Ly-$\alpha$ forest, galaxy counts, etc.). This finding reopens the region of lighter sterile neutrinos. The new region may be explored with the next generation of X-ray telescopes searching for the inherent peak signature provided by the dark matter sterile neutrino radiative decays in the Galaxy.
