Leptonic Dirac CP violation predictions from residual discrete symmetries

Nuclear Physics B. 2016;902(C):1-57 DOI 10.1016/j.nuclphysb.2015.10.020

 

Journal Homepage

Journal Title: Nuclear Physics B

ISSN: 0550-3213 (Print); 1873-1562 (Online)

Publisher: Elsevier

LCC Subject Category: Science: Physics: Nuclear and particle physics. Atomic energy. Radioactivity

Country of publisher: Netherlands

Language of fulltext: English

Full-text formats available: PDF, HTML

 

AUTHORS

I. Girardi (SISSA/INFN, Via Bonomea 265, 34136 Trieste, Italy)
S.T. Petcov (SISSA/INFN, Via Bonomea 265, 34136 Trieste, Italy)
Alexander J. Stuart (SISSA/INFN, Via Bonomea 265, 34136 Trieste, Italy)
A.V. Titov (SISSA/INFN, Via Bonomea 265, 34136 Trieste, Italy)

EDITORIAL INFORMATION

Peer review

Editorial Board

Instructions for authors

Time From Submission to Publication: 12 weeks

 

Abstract | Full Text

Assuming that the observed pattern of 3-neutrino mixing is related to the existence of a (lepton) flavour symmetry, corresponding to a non-Abelian discrete symmetry group Gf, and that Gf is broken to specific residual symmetries Ge and Gν of the charged lepton and neutrino mass terms, we derive sum rules for the cosine of the Dirac phase δ of the neutrino mixing matrix U. The residual symmetries considered are: i) Ge=Z2 and Gν=Zn, n>2 or Zn×Zm, n,m≥2; ii) Ge=Zn, n>2 or Zn×Zm, n,m≥2 and Gν=Z2; iii) Ge=Z2 and Gν=Z2; iv) Ge is fully broken and Gν=Zn, n>2 or Zn×Zm, n,m≥2; and v) Ge=Zn, n>2 or Zn×Zm, n,m≥2 and Gν is fully broken. For given Ge and Gν, the sum rules for cos⁡δ thus derived are exact, within the approach employed, and are valid, in particular, for any Gf containing Ge and Gν as subgroups. We identify the cases when the value of cos⁡δ cannot be determined, or cannot be uniquely determined, without making additional assumptions on unconstrained parameters. In a large class of cases considered the value of cos⁡δ can be unambiguously predicted once the flavour symmetry Gf is fixed. We present predictions for cos⁡δ in these cases for the flavour symmetry groups Gf=S4, A4, T′ and A5, requiring that the measured values of the 3-neutrino mixing parameters sin2⁡θ12, sin2⁡θ13 and sin2⁡θ23, taking into account their respective 3σ uncertainties, are successfully reproduced.