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Flavor symmetries, leptogenesis and the absolute neutrino mass scale

Flavor symmetries, leptogenesis and the absolute neutrino mass scale
Flavor symmetries, leptogenesis and the absolute neutrino mass scale
We study the interplay between flavor symmetries and leptogenesis in the case when the scale of flavor symmetry breaking is higher than the scale at which lepton number is violated. We show that when the heavy Majorana neutrinos belong to an irreducible representation of the flavor group, all the leptogenesis CP asymmetries vanish in the limit of exact symmetry.

In the case of reducible representations we identify a general condition that, if satisfied, guarantees the same result. We then focus on the case of a model in which an A4 flavor symmetry yields a drastic reduction in the number of free parameters, implying that at leading order several quantities are only a function of the lightest neutrino mass ml, which in turn is strongly constrained. For normal ordering (NO) we find ml simeq (0.0044÷0.0056) eV while for inverted ordering (IO) mlgtrsim0.017 eV. For the 0?2? decay parameter this yields |mee| simeq (0.006÷0.007) eV (NO) and |mee|gsim0.017 eV (IO). We show that the leptogenesis CP asymmetries only depend on ml, on a single non-hierarchical Yukawa coupling y, and on two parameters that quantify the flavor symmetry breaking effects, and we argue that the unflavored regime for leptogenesis is strongly preferred in our model, thus realizing a rather predictive scenario.

Performing a calculation of the matter-antimatter asymmetry we find that for NO the observed value is easily reproduced for natural values of the symmetry breaking parameters. For IO successful leptogenesis is possible for a limited choice of the parameters implying rather large reheating temperatures Trehgtrsim5 × 1013 GeV.
discrete and finite symmetries, neutrino physics, osmology of theories beyond the SM, CP violation
1-35
Bertuzzo, Enrico
d35bf853-fe74-40f7-8480-196664afd2d5
Di Bari, Pasquale
3fe21e59-0eff-41bc-8faa-fdd817146418
Feruglio, Ferruccio
275f8c70-ed53-42b9-9ab4-cfccca47ca7a
Nardi, Enrico
f8d2f6ab-865b-41fb-81a3-469e3c5eb1ba
Bertuzzo, Enrico
d35bf853-fe74-40f7-8480-196664afd2d5
Di Bari, Pasquale
3fe21e59-0eff-41bc-8faa-fdd817146418
Feruglio, Ferruccio
275f8c70-ed53-42b9-9ab4-cfccca47ca7a
Nardi, Enrico
f8d2f6ab-865b-41fb-81a3-469e3c5eb1ba

Bertuzzo, Enrico, Di Bari, Pasquale, Feruglio, Ferruccio and Nardi, Enrico (2009) Flavor symmetries, leptogenesis and the absolute neutrino mass scale. Journal of High Energy Physics, 11 (36), 1-35. (doi:10.1088/1126-6708/2009/11/036).

Record type: Article

Abstract

We study the interplay between flavor symmetries and leptogenesis in the case when the scale of flavor symmetry breaking is higher than the scale at which lepton number is violated. We show that when the heavy Majorana neutrinos belong to an irreducible representation of the flavor group, all the leptogenesis CP asymmetries vanish in the limit of exact symmetry.

In the case of reducible representations we identify a general condition that, if satisfied, guarantees the same result. We then focus on the case of a model in which an A4 flavor symmetry yields a drastic reduction in the number of free parameters, implying that at leading order several quantities are only a function of the lightest neutrino mass ml, which in turn is strongly constrained. For normal ordering (NO) we find ml simeq (0.0044÷0.0056) eV while for inverted ordering (IO) mlgtrsim0.017 eV. For the 0?2? decay parameter this yields |mee| simeq (0.006÷0.007) eV (NO) and |mee|gsim0.017 eV (IO). We show that the leptogenesis CP asymmetries only depend on ml, on a single non-hierarchical Yukawa coupling y, and on two parameters that quantify the flavor symmetry breaking effects, and we argue that the unflavored regime for leptogenesis is strongly preferred in our model, thus realizing a rather predictive scenario.

Performing a calculation of the matter-antimatter asymmetry we find that for NO the observed value is easily reproduced for natural values of the symmetry breaking parameters. For IO successful leptogenesis is possible for a limited choice of the parameters implying rather large reheating temperatures Trehgtrsim5 × 1013 GeV.

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Published date: 9 November 2009
Keywords: discrete and finite symmetries, neutrino physics, osmology of theories beyond the SM, CP violation
Organisations: High Energy Physics

Identifiers

Local EPrints ID: 152715
URI: https://eprints.soton.ac.uk/id/eprint/152715
PURE UUID: a1bf2fd5-c4d4-4daf-94c8-6bf3d3150c69

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Date deposited: 17 May 2010 08:06
Last modified: 28 Oct 2019 21:40

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