Sterile neutrino dark matter production in lepton asymmetric universe and its observational implications

概要

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Sterile neutrino with masses of the keV scale is a fascinating candidate for dark matter (DM). They can be produced via neutrino oscillations involving the Standard model neutrinos (“active” neutrinos), which are in thermal equilibrium in the early universe. Especially, in the presence of significant neutrino-antineutrino asymmetry, the production rate of the sterile neutrinos is resonantly enhanced and we can successfully account for all dark matter consistent with observational constraints.

In this seminar, we first present a comprehensive numerical analysis of the resonant production scenario and explore the consistency with current observations.

Secondly, we examine a leptogenesis scenario that can naturally generate the neutrino-antineutrino asymmetry consistent with the resonant production of sterile neutrino DM. We demonstrate that this can be realized within the framework of Affleck-Dine leptogenesis, based on the minimal supersymmetric Standard Model (MSSM). In our setup, spherical clumps of the slepton field—known as Q-balls—form and eventually decay into lepton asymmetric Standard model plasma.

Furthermore, in the above setup, Q-balls dominate the cosmic energy density and finally decay rapidly into radiation, triggering sudden reheating. This sudden reheating causes subhorizon modes of the gravitational potential to oscillate with large amplitudes, and then a significant amount of the gravitational waves (GWs) are produced by curvature perturbations at second order. Based on this idea, we discuss the testability of the scenario with the future GW observations.

This presentation is mainly based on arXiv:2402.11902, but includes some updates on the analysis.