Scalar neutrino as asymmetric dark matter: radiative neutrino mass and leptogenesis

Abstract

In the minimal supersymmetric standard model, the scalar neutrino ν˜_L has odd R parity, yet it has long been eliminated as a dark-matter candidate because it scatters elastically off nuclei through the Z boson, yielding a cross section many orders of magnitude above the experimental limit. We show how it can be reinstated as a dark-matter candidate by splitting the masses of its real and imaginary parts in an extension of the minimal supersymmetric standard model with scalar triplets. As a result, radiative neutrino masses are generated. This severely constrains the U(1) and SU(2) gaugino masses as a function of the ν˜_L mass, which is bounded by the 2011 XENON100 data to be above 125 GeV. Whereas a ν˜-ν˜^* asymmetry is created from the decay of a heavy scalar triplet together with a lepton asymmetry, it gets washed out by ν˜-ν˜^* oscillations after the electroweak phase transition. However, ν˜₂ then decays into ν˜₁νν̅ fast enough so that only ν˜₁ survives as dark matter today.