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Title: Type II Leptogenesis

Abstract

We discuss leptogenesis via the out-of-equilibrium decay of the lightest right-handed neutrino in type II see-saw scenarios, where, in addition to the type I see-saw, an additional direct mass term for the light neutrinos is present. The results for the decay asymmetries are presented in theories where this additional contribution stems from the induced vev of a Higgs triplet, and furthermore in an effective, model independent approach. We emphasize that when the neutrino mass scale increases, type II leptogenesis can be more efficient than for hierarchical light neutrinos, in sharp contrast to the type I see-saw cwhere successful thermal leptogenesis even imposes a bound on the neutrino mass scale of about 0.1 eV.

Authors:
 [1];  [2]
  1. Departamento de Fisica Teorica C-XI, Universidad Autonoma de Madrid, Cantoblanco, E-28049 Madrid (Spain)
  2. (Spain)
Publication Date:
OSTI Identifier:
20900805
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 881; Journal Issue: 1; Conference: CICHEP II: Cairo international conference on high energy physics, Cairo (Egypt), 14-17 Jan 2006; Other Information: DOI: 10.1063/1.2435292; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ASYMMETRY; HIGGS BOSONS; HIGGS MODEL; MASS; NEUTRINOS; PARTICLE DECAY; TRIPLETS

Citation Formats

Antusch, Stefan, and Instituto de Fisica Teorica C-XVI, Universidad Autonoma de Madrid, Cantoblanco, E-28049 Madrid. Type II Leptogenesis. United States: N. p., 2007. Web. doi:10.1063/1.2435292.
Antusch, Stefan, & Instituto de Fisica Teorica C-XVI, Universidad Autonoma de Madrid, Cantoblanco, E-28049 Madrid. Type II Leptogenesis. United States. doi:10.1063/1.2435292.
Antusch, Stefan, and Instituto de Fisica Teorica C-XVI, Universidad Autonoma de Madrid, Cantoblanco, E-28049 Madrid. Fri . "Type II Leptogenesis". United States. doi:10.1063/1.2435292.
@article{osti_20900805,
title = {Type II Leptogenesis},
author = {Antusch, Stefan and Instituto de Fisica Teorica C-XVI, Universidad Autonoma de Madrid, Cantoblanco, E-28049 Madrid},
abstractNote = {We discuss leptogenesis via the out-of-equilibrium decay of the lightest right-handed neutrino in type II see-saw scenarios, where, in addition to the type I see-saw, an additional direct mass term for the light neutrinos is present. The results for the decay asymmetries are presented in theories where this additional contribution stems from the induced vev of a Higgs triplet, and furthermore in an effective, model independent approach. We emphasize that when the neutrino mass scale increases, type II leptogenesis can be more efficient than for hierarchical light neutrinos, in sharp contrast to the type I see-saw cwhere successful thermal leptogenesis even imposes a bound on the neutrino mass scale of about 0.1 eV.},
doi = {10.1063/1.2435292},
journal = {AIP Conference Proceedings},
number = 1,
volume = 881,
place = {United States},
year = {Fri Jan 12 00:00:00 EST 2007},
month = {Fri Jan 12 00:00:00 EST 2007}
}
  • In the framework of the type II seesaw mechanism we propose two simple but instructive ansaetze for neutrino mixing and leptogenesis. In each ansatz, the effective Majorana neutrino mass matrix is composed of two parts--the part with Z{sub 2} symmetry arises from the ordinary type I seesaw mechanism and the part with S{sub 3} symmetry arises from an additional Higgs triplet vacuum expectation value. The two ansaetze can simultaneously account for the current neutrino oscillation data and the cosmological baryon number asymmetry via leptogenesis.
  • A possible interplay of both terms in the type II seesaw formula is illustrated by presenting a novel way to generate deviations from exact bimaximal neutrino mixing. In the type II seesaw mechanism with dominance of the noncanonical SU(2){sub L} triplet term, the conventional seesaw term can naturally give a small contribution to the neutrino mass matrix. Nevertheless, if the triplet term corresponds to the bimaximal mixing scheme in the normal hierarchy, the small contribution of the conventional seesaw term naturally generates nonmaximal solar neutrino mixing. Atmospheric neutrino mixing is also reduced from maximal, corresponding to 1-sin{sup 2}2{theta}{sub 23} ofmore » order 0.01. Also, small but nonvanishing U{sub e3} of order 0.001 is obtained. It is also possible that the {delta}m{sup 2} responsible for solar neutrino oscillations is induced by the small conventional seesaw term. Larger deviations from zero U{sub e3} and from maximal atmospheric neutrino mixing are then expected. This scenario links the small ratio of the solar and atmospheric {delta}m{sup 2} with the deviation from maximal solar neutrino mixing. We comment on leptogenesis in this scenario and compare the contributions to the decay asymmetry of the heavy Majorana neutrinos as induced by themselves and by the triplet.« less
  • The presence of the triplet {delta}{sub L} in left-right symmetric theories leads to type-II seesaw mechanism for the neutrino masses. In these models, assuming a normal mass hierarchy for the heavy Majorana neutrinos, we derive a lower bound on the mass of the lightest of heavy Majorana neutrinos from the leptogenesis constraint. From this bound we establish a consistent picture for the hierarchy of heavy Majorana neutrinos in a class of left-right symmetric models in which we identify the neutrino Dirac mass matrix with that of Fritzsch type charged lepton mass matrix. It is shown that these values are compatiblemore » with the current neutrino oscillation data.« less
  • Current experimental data allow the zero value for one neutrino mass, either m{sub 1}=0 or m{sub 3}=0. This observation implies that a realistic neutrino mass texture can be established by starting from the limit (a) m{sub 1}=m{sub 2}=0 and m{sub 3}{ne}0 or (b) m{sub 1}=m{sub 2}{ne}0 and m{sub 3}=0. In both cases, we may introduce a particular perturbation which ensures the resultant neutrino mixing matrix to be the tribimaximal mixing pattern or its viable variations with all entries being formed from small integers and their square roots. We find that it is natural to incorporate this kind of neutrino massmore » matrix in the minimal type-II seesaw model with only one heavy right-handed Majorana neutrino N in addition to the SU(2){sub L} Higgs triplet {delta}{sub L}. We show that it is possible to account for the cosmological baryon number asymmetry in the m{sub 3}=0 case via thermal leptogenesis, in which the one-loop vertex correction to N decays is mediated by {delta}{sub L} and the CP-violating asymmetry of N decays is attributed to the electron flavor.« less
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