Title: Advantages of unity with SU(4)-color: Reflections through neutrino oscillations, baryogenesis and proton decay

Abstract

As a tribute to Abdus Salam, I recall the initiation in 1972-73 of the idea of grand unification based on the view that lepton number is the fourth color. Motivated by aesthetic demands, these attempts led to the suggestion that the existing SU (2) x U (1) symmetry be extended minimally to the quark-lepton and left-right symmetric non-Abelian gauge structure G (2,2,4) = SU (2)_L x SU (2)_R x SU (4)-color. This served to unify members of a family within a single L-R self-conjugate multiplet. It also explained: the quantization of electric charge, the co-existence of quarks and leptons, and that of their three basic forces $$-$$ weak, electromagnetic, and strong $$-$$ while providing the appealing possibility that nature is fundamentally left-right symmetric (parity-conserving). The minimal extension of the symmetry G (2,2,4) to a simple group is given by the attractive symmetry SO (10) that came a year later. The advantages of the core symmetry G (2,2,4), including those listed above (which are of course retained by SO (10) as well), are noted. These include the introductions of: (i) the right-handed neutrino as a compelling member of each family, (ii) (B-L) as a local symmetry, and (iii) the mass relation m (ν^τ) _Dirac = m_top (M_GUT). These three features, all arising due to SU(4)-color, as well as the gauge coupling uni cation scale (identi ed with the (B-L)- breaking scale), are crucially needed to understand the tiny mass-scales of the neutrino oscillations within the seesaw mechanism, and to implement successfully the mechanism of baryogenesis via leptogenesis. Implications of a well-motivated class of models based on supersymmetric SO(10) or a string-unified G(2, 2, 4) symmetry in 4D for (a) gauge coupling uni cation, (b) fermion masses and mixings, (c) neutrino osillations, (d) baryogenesis via leptogenesis, and last but not least (e) proton decay are presented. Recent works on the latter providing upper limits on proton lifetimes suggest that the potential for discovery of proton decay in the next-generation detectors would be high.

Authors:

Pati, Jogesh C. ^[1]

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+ Show Author Affiliations

1. SLAC National Accelerator Lab., Menlo Park, CA (United States)

Publication Date:

Fri Mar 24 00:00:00 EDT 2017

Research Org.:

SLAC National Accelerator Lab., Menlo Park, CA (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1360752

Report Number(s):

SLAC-PUB-16937
Journal ID: ISSN 0217-751X

Grant/Contract Number:  

AC02-76SF00515

Resource Type:

Accepted Manuscript

Journal Name:

International Journal of Modern Physics A

Additional Journal Information:

Journal Volume: 32; Journal Issue: 09; Journal ID: ISSN 0217-751X

Publisher:

World Scientific

Country of Publication:

United States

Language:

English

Subject:

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS