Leptogenesis and Neutrino Masses Via Pseudo-Dirac Gauginos

Abstract

In a $U(1)_{R-L}$-symmetric supersymmetric model, pseudo-Dirac bino and wino can act like right-handed neutrinos, generating the light neutrino masses through a hybrid Type I + III inverse seesaw mechanism. We investigate such a model to accommodate the baryon asymmetry of the universe together with neutrino masses. A pseudo-Dirac gaugino goes under particle-antiparticle oscillations. Possible $CP$ violation in bino decays, induced by mixing with the neutrinos, can be enhanced in bino--antibino oscillations. Focusing on a long-lived bino, we show that its oscillations and decays can generate the observed baryon asymmetry while the wino is responsible for generating the neutrino masses. This mechanism requires a decoupled mass spectrum with a bino of mass $M_{\tilde{B}}\sim O({\rm TeV})$ and sfermions with mass $M_{\rm sf}\gtrsim 25$ TeV. Furthermore, for the bino to decay out-of-equilibrium before the electroweak sphalerons turn off, the messenger scale needs to be $Λ_M \sim O(10^7~ {\rm TeV})$. We discuss the displaced vertex signals at the LHC resulting from such a high messenger scale.