Abstract
In the canonical seesaw mechanism of neutrino mass, lepton number is only multiplicatively conserved, which enables the important phenomenon of leptogenesis to occur, as an attractive explanation of the present baryon asymmetry of the Universe. A parallel possibility, hitherto unrecognized, also holds for baryon number and baryogenesis. This new idea is shown to be naturally realized in the context of a known supersymmetric string-inspired extension of the Standard Model, based on E6 particle content, and having an extra U(1)N gauge symmetry. Within this framework, two-loop radiative neutrino masses are also possible, together with a new form of very long-lived matter.
Highlights
In the canonical seesaw mechanism of neutrino mass, lepton number is only multiplicatively conserved, which enables the important phenomenon of leptogenesis to occur, as an attractive explanation of the present baryon asymmetry of the Universe
The only interactions of Ni are with the lepton doublets and the Higgs doublet (φ+, φ0)
Sphaleron interactions will modify this pure B asymmetry into a B − L asymmetry in exact analogy to what happens to a pure L asymmetry in the case of leptogenesis. This new idea of multiplicatively conserved baryon number and baryogenesis turns out to be naturally realized in the context of a supersymmetric string-inspired extension of the Standard Model (SM) proposed some time ago [7], with many interesting features in its own right [8, 9]
Summary
In the canonical seesaw mechanism of neutrino mass, lepton number is only multiplicatively conserved, which enables the important phenomenon of leptogenesis to occur, as an attractive explanation of the present baryon asymmetry of the Universe. A parallel and elegant possibility, i.e. multiplicatively conserved baryon number and baryogenesis, is proposed and shown to be naturally realized in the framework of a known supersymmetric string-inspired extension [7] of the Standard Model (SM), as detailed below. As the Universe expands and cools, the out-of-equilibrium decays of N1 (i.e. the lightest Ni) into l−φ+ and l+φ− establish a lepton (L) asymmetry.
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