Inverse see-saw, leptogenesis, observable proton decay and $Δ^{\pm\pm}_{\rm R}$ in SUSY SO(10) with heavy W_R

Abstract

We explore low-scale leptogenesis in a class of supersymmetric SO(10) models using extra singlet neutrinos and the Higgs representations {126}_H\oplus {\ovl{126}}_H as well as {16}_H \oplus {\bar {16}}_H. A singlet neutrino, which can be as light as 10^5-10^6 GeV, decays through its small mixings with right-handed neutrinos creating a lepton asymmetry which is shown to be flavor dependent. While the doublet vacuum expectation value in {\ovl{16}}_H triggers the generation of desired mixings, it also induces a large RH triplet vev that breaks the LR intermediate gauge symmetry and gives large RH neutrino masses. Manifest unification of gauge couplings and generation of heavy RH neutrino masses are achieved by renormalizable interactions. The canonical (Type-I) see-saw contributions to the light neutrino mass matrix cancel out while the Type-II see-saw contribution is negligible. Determining the parameters of the dominant inverse see-saw formula using the underlying quark-lepton symmetry and neutrino oscillation data, we show how leptogenesis under the gravitino constraint is successfully implemented. New formulas for the decay rate and the asymmetry parameter are derived leading to baryon asymmetry within the observed range. The model is found to work for hierarchical as well as inverted hierarchical light neutrino masses. Testable predictions of the model are RH doubly charged Higgs bosons which may be leptophilic and accessible to the Tevatron, LHC or a linear collider. In a model-independent manner, the Drell-Yan pair production cross section is shown to be bounded between 59%-79% of their left-handed counterparts with same mass. In contrast to single-step breaking SUSY GUTs, which predict a long proton lifetime for p\to e^+π^0, here this lifetime is substantially reduced, bringing it within one order of the current experimental limit.