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Type II leptogenesis and the neutrino mass scale

Type II leptogenesis and the neutrino mass scale
Type II leptogenesis and the neutrino mass scale
We discuss the effect of the neutrino mass scale on baryogenesis via the out-of-equilibrium decay of the lightest right-handed (s)neutrinos in type II see–saw models. We calculate the type II contributions to the decay asymmetries for minimal scenarios based on the Standard Model and on the Minimal Supersymmetric Standard Model, where the additional direct mass term for the neutrinos arises from a Higgs triplet vacuum expectation value. The result in the supersymmetric case is new and we correct the previous result in the scenario based on the Standard Model. We confirm and generalize our results by calculating the decay asymmetries in an effective approach, which is independent of the realization of the type II contribution. We derive a general upper bound on the decay asymmetry in type II see–saw models and find that it increases with the neutrino mass scale, in sharp contrast to the type I case which leads to an upper bound of about 0.1 eV on the neutrino mass scale. We find a lower bound on the mass of the lightest right-handed neutrino, significantly below the corresponding type I bound for partially degenerate neutrinos. This lower bound decreases with increasing neutrino mass scale, making leptogenesis more consistent with the gravitino constraints in supersymmetric models.
0370-2693
199-207
Antusch, S.
5c4a4555-199c-4b90-9590-f4c392ee850c
King, S.F.
f8c616b7-0336-4046-a943-700af83a1538
Antusch, S.
5c4a4555-199c-4b90-9590-f4c392ee850c
King, S.F.
f8c616b7-0336-4046-a943-700af83a1538

Antusch, S. and King, S.F. (2004) Type II leptogenesis and the neutrino mass scale. Physics Letters B, 597 (2), 199-207. (doi:10.1016/j.physletb.2004.07.009).

Record type: Article

Abstract

We discuss the effect of the neutrino mass scale on baryogenesis via the out-of-equilibrium decay of the lightest right-handed (s)neutrinos in type II see–saw models. We calculate the type II contributions to the decay asymmetries for minimal scenarios based on the Standard Model and on the Minimal Supersymmetric Standard Model, where the additional direct mass term for the neutrinos arises from a Higgs triplet vacuum expectation value. The result in the supersymmetric case is new and we correct the previous result in the scenario based on the Standard Model. We confirm and generalize our results by calculating the decay asymmetries in an effective approach, which is independent of the realization of the type II contribution. We derive a general upper bound on the decay asymmetry in type II see–saw models and find that it increases with the neutrino mass scale, in sharp contrast to the type I case which leads to an upper bound of about 0.1 eV on the neutrino mass scale. We find a lower bound on the mass of the lightest right-handed neutrino, significantly below the corresponding type I bound for partially degenerate neutrinos. This lower bound decreases with increasing neutrino mass scale, making leptogenesis more consistent with the gravitino constraints in supersymmetric models.

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Published date: 2004

Identifiers

Local EPrints ID: 56976
URI: http://eprints.soton.ac.uk/id/eprint/56976
ISSN: 0370-2693
PURE UUID: c7ade06b-ed74-4d4e-89c8-ed119ced48f3

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Date deposited: 13 Aug 2008
Last modified: 15 Mar 2024 11:04

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Contributors

Author: S. Antusch
Author: S.F. King

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