Naturalness in soft leptogenesis and gravitino mass bound due to primordial black holes

Abstract

If sneutrinos are produced through primordial black hole (PBH) evaporation, then some interesting features of soft leptogenesis in the Minimal Supersymmetric Standard Model with heavy right-handed neutrinos, are found. The required baryonic asymmetry could be possible from the decays of sneutrinos, for the soft SUSY breaking trilinear $A$ and bilinear $B$ parameters around the electroweak scale. The resonance condition in soft leptogenesis is not required. The allowed regions of different relevant parameters are discussed in detail. Using experimental constraints from collider searches on heavy leptons, the lower bound on the right-handed neutrino mass is found to be around 300 GeV with Yukawa coupling lesser than about 0.4. The allowed region of the typical mass scale of some supersymmetric particles and the $\left|A\right|$ parameter is also shown from the experimental constraint on the branching ratio for $\mu \to e\gamma$ in MEG II search. Depending on PBH mass, bounds on the mass of gravitinos, produced from PBH evaporation, is discussed and gravitino mass around the electroweak scale is found to be possible only for unstable gravitino.