Conditions for a successful right-handed Majorana sneutrino curvaton

Abstract

We consider the conditions which must be satisfied for a Majorana RH sneutrino, a massive right-handed (RH) sneutrino associated with the see-saw mechanism of Majorana neutrino masses, to play the role of the curvaton. Planck-scale suppressed non-renormalizable terms in the RH neutrino superpotential must be eliminated to a high order if the RH sneutrino curvaton is to dominate the energy density before it decays, which can be achieved via an R-symmetry which is broken to R-parity by the Giudice-Maseiro mechanism. In order to satisfy the thermalization constraint, one RH neutrino mass eigenstate must have small Yukawa couplings to the Higgs and lepton doublets, corresponding to a lightest neutrino mass m_{nu_{1}} < 10^{-3} eV. A time-dependent lepton asymmetry will be induced in the RH sneutrino condensate by the Affleck-Dine mechanism driven by SUSY breaking B-terms associated with the RH neutrino masses. Requiring that the resulting baryon asymmetry and isocurvature perturbations are acceptably small imposes an upper bound on the RH neutrino mass. We show that a scenario consistent with all constraints is obtained for a RH neutrino mass in the range 10^{2} - 10^{4} GeV when the RH sneutrino decay temperature is greater than 100 GeV and lightest neutrino mass m_{nu_{1}} approx 10^{-3} GeV. Larger RH neutrino masses are possible for smaller m_{nu_{1}}. The resulting scenario is generally consistent with a solution of the cosmic string problem of D-term inflation.