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Title: {mu}-{tau} symmetry and radiatively generated leptogenesis

Abstract

We consider a {mu}-{tau} symmetry in neutrino sectors realized at the GUT scale in the context of a seesaw model. In our scenario, the exact {mu}-{tau} symmetry realized in the basis where the charged lepton and heavy Majorana neutrino mass matrices are diagonal leads to vanishing lepton asymmetries. We find that, in the minimal supersymmetric extension of the seesaw model with large tan{beta}, the renormalization group (RG) evolution from the GUT scale to seesaw scale can induce a successful leptogenesis even without introducing any symmetry breaking terms by hand, whereas such RG effects lead to tiny deviations of {theta}{sub 23} and {theta}{sub 13} from {pi}/4 and zero, respectively. It is shown that the right amount of the baryon asymmetry {eta}{sub B} can be achieved via so-called resonant leptogenesis, which can be realized at rather low seesaw scale with large tan{beta} in our scenario so that the well-known gravitino problem is safely avoided.

Authors:
; ;  [1];  [2]
  1. Department of Physics, Yonsei University, Seoul 120-749 (Korea, Republic of)
  2. Center for Quantum Spacetime, Sogang University, Seoul 121-742 (Korea, Republic of)
Publication Date:
OSTI Identifier:
20933214
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 75; Journal Issue: 1; Other Information: DOI: 10.1103/PhysRevD.75.013012; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ASYMMETRY; BARYONS; MUON NEUTRINOS; SUPERSYMMETRY; SYMMETRY BREAKING; TAU NEUTRINOS

Citation Formats

Ahn, Y. H., Kim, C. S., Lee, Jake, and Kang, Sin Kyu. {mu}-{tau} symmetry and radiatively generated leptogenesis. United States: N. p., 2007. Web. doi:10.1103/PHYSREVD.75.013012.
Ahn, Y. H., Kim, C. S., Lee, Jake, & Kang, Sin Kyu. {mu}-{tau} symmetry and radiatively generated leptogenesis. United States. doi:10.1103/PHYSREVD.75.013012.
Ahn, Y. H., Kim, C. S., Lee, Jake, and Kang, Sin Kyu. Mon . "{mu}-{tau} symmetry and radiatively generated leptogenesis". United States. doi:10.1103/PHYSREVD.75.013012.
@article{osti_20933214,
title = {{mu}-{tau} symmetry and radiatively generated leptogenesis},
author = {Ahn, Y. H. and Kim, C. S. and Lee, Jake and Kang, Sin Kyu},
abstractNote = {We consider a {mu}-{tau} symmetry in neutrino sectors realized at the GUT scale in the context of a seesaw model. In our scenario, the exact {mu}-{tau} symmetry realized in the basis where the charged lepton and heavy Majorana neutrino mass matrices are diagonal leads to vanishing lepton asymmetries. We find that, in the minimal supersymmetric extension of the seesaw model with large tan{beta}, the renormalization group (RG) evolution from the GUT scale to seesaw scale can induce a successful leptogenesis even without introducing any symmetry breaking terms by hand, whereas such RG effects lead to tiny deviations of {theta}{sub 23} and {theta}{sub 13} from {pi}/4 and zero, respectively. It is shown that the right amount of the baryon asymmetry {eta}{sub B} can be achieved via so-called resonant leptogenesis, which can be realized at rather low seesaw scale with large tan{beta} in our scenario so that the well-known gravitino problem is safely avoided.},
doi = {10.1103/PHYSREVD.75.013012},
journal = {Physical Review. D, Particles Fields},
number = 1,
volume = 75,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • If an exact {mu}{r_reversible}{tau} symmetry is the explanation of the maximal atmospheric neutrino mixing angle, it has interesting implications for the origin of matter via leptogenesis in models where small neutrino masses arise via the seesaw mechanism. For seesaw models with two right-handed neutrinos (N{sub {mu}},N{sub {tau}}), lepton asymmetry vanishes in the exact {mu}{r_reversible}{tau} symmetric limit, even though there are nonvanishing Majorana phases in the neutrino mixing matrix. On the other hand, for three right-handed neutrino models, lepton asymmetry is nonzero and is given directly by the solar mass difference square. We also find an upper bound on the lightestmore » neutrino mass.« less
  • Nonvanishing U{sub e3} has been theoretically related to a certain flavor symmetry breaking in the neutrino sector. We propose a scenario to break the {mu}-{tau} symmetry so as to accommodate the nonvanishing U{sub e3}. Our scenario is constructed in the context of a seesaw model, and the {mu}-{tau} symmetry breaking is achieved by introducing a CP phase in the Dirac Yukawa matrix. We also show how the deviation of {theta}{sub 23} from the maximal mixing and nonvanishing U{sub e3} depend on the CP phase. Neutrino mixings and the neutrino mass-squared differences are discussed, and the amplitude in neutrinoless double betamore » decay m{sub ee} are also predicted. We found that a tiny breaking of the {mu}-{tau} symmetry due to mass splitting between two degenerate heavy Majorana neutrinos on top of the Dirac CP phase can lead to successful leptogenesis. We examine how leptogenesis can be related with low energy neutrino measurement, and show that our predictions for U{sub e3} and m{sub ee} can be constrained by the current observation of baryon asymmetry.« less
  • Continuous U(1){sub {mu}}-L{sub {tau}} symmetry can generate quasidegenerate mass spectrum for both left handed light and right handed heavy Majorana neutrinos assuming that the symmetry preserving nonzero parameters are nearly same. There is an accidental {mu}{tau} exchange symmetry in the light and heavy neutrino Majorana mass terms. This implies {theta}{sub 13}=0 and {theta}{sub 23}=({pi}/4). In addition it generates another zero mixing angle and one zero mass difference. We restrict ourselves to type-I See-Saw mechanism for generation of light neutrino mass. We have found that under U(1){sub L{sub {mu}}-L{sub {tau}}} symmetry cosmological lepton asymmetry vanishes. We break U(1){sub L{sub {mu}}-L{sub {tau}}}more » such a way that the {mu}{tau} exchange symmetry preserves in the neutrino sector. We have seen that light neutrino phenomenology can be explained under soft breaking of this symmetry. We have observed that softness of this symmetry breaking depends on the degeneracy of the light neutrino mass spectrum. Quasidegeneracy of right handed neutrino mass spectrum opens an option for resonant leptogenesis. The degeneracy of the right handed neutrino mass spectrum is restricted through light neutrino data. We observed that for generation of right sized baryon asymmetry common neutrino mass scale m{sub 0} have to be of the order of {radical}({delta}m{sub atm}{sup 2}) and corresponding right handed neutrino mass scale have to be nearly 10{sup 13} GeV. We also have discussed the effect of RG evolution on light neutrino spectrum and also on baryon asymmetry.« less
  • Leptogenesis is studied in a seesaw model with {mu}-{tau} symmetry for SU{sub L}(2)-singlet right-handed neutrinos. It is shown that lepton asymmetry is not zero and is given by the square of the solar neutrino mass difference and can be of the right order of magnitude. Further it involves the same Majorana phase which appears in the neutrinoless double {beta}-decay. In this framework one of the right-handed seesaw partners of light neutrinos can be made massless. This can be identified with a sterile neutrino, once it acquires a tiny mass ({approx_equal}1 eV) when {mu}-{tau} symmetry is broken in the right-handed neutrinomore » sector. The above mentioned sterile neutrino together with another one can be identified to explain the MiniBooNE and LSND results. The light 5x5 neutrino mass matrix is completely fixed if CP is conserved and so is the effective mass for neutrinoless double {beta}-decay.« less
  • The degenerate leptogenesis is studied when the degeneracy in two of the heavy right-handed neutrinos [the third one is irrelevant if {mu}-{tau} symmetry is assumed] is due to L{identical_to}(L{sub e}-L{sub {mu}-}L{sub {tau}}) discrete symmetry. It is shown that a sizable leptogenesis asymmetry ({epsilon}{>=}10{sup -6}) is possible. The level of degeneracy required also predicts the Majorana phase needed for the asymmetry and this prediction is testable since it is the same phase, which appears in the double {beta} decay. Implications of nonzero reactor angle {theta}{sub 13} are discussed. It is shown that the contribution from sin{sup 2{theta}}{sub 13} to the leptogenesismore » asymmetry parameter may even dominate. An accurate measurement of sin{sup 2{theta}}{sub 13} would have important implications for the mass degeneracy of heavy right-handed neutrinos.« less