A Unified Picture with Neutrino As a Central Feature

Abstract

In the first part of this talk it is discussed why observed neutrino oscillations (which suggest the existence of right-handed neutrinos with certain Dirac and Majorana masses) seem to select out the route to higher unification based on the symmetry SU(4)-color. This in turn selects out the effective symmetry in 4D near the GUT/string scale to be either SO(10) or minimally G(224)= SU(2)_L\times SU(2)_R \times SU(4)^c. The same conclusion is reached by the likely need for leptogenesis as the means for baryogenesis and also by the success of certain fermion mass-relations including m_b(M_{GUT})\approx m_τ, together with m(ν^τ)_{Dirac}\approx m_{top}(M_{GUT}). In the second part, an attempt is made to provide a unified picture of a set of diverse phenomena based on an effective G(224) symmetry or SO(10), possessing supersymmetry. The phenomena in question include: (a) fermion masses and mixings, (b) neutrino oscillations, (c) CP non-conservation, (d) flavor violations in quark and lepton sectors, as well as (e) baryogenesis via leptogenesis. Including SM and SUSY contributions, the latter being sub-dominant, the framework correctly accounts for Δm_K, Δm_{B_d}, S(B_d -> J/ψK_s) and ε_K, and predicts S(B_d-> ϕK_s) to be in the range +(0.65-0.73), close to the SM-prediction. It also quite plausibly accounts for the observed baryon excess Y_B\approx 10^{-10}. Furthermore the model predicts enhanced rates for mu -> e gamma, tau-> mu gamma and mu N-> e N and also measurable electric dipole moment for the neutron. Expectations arising within the same framework for proton decay are summarized at the end. It is stressed that the potential for discovering proton decay in a megaton-size detector would be high.