Implications of μ-τ flavored CP symmetry of leptons

Abstract

Abstract:We discuss gauge models incorporating µ-τ flavored CP symmetry (called CP µτ in the text) in combination with L µ − L τ invariance to understand neutrino mixings and discuss their phenomenological implications. We show that viable leptogenesis in this setting requires that the lightest right-handed neutrino mass must be between 10 9 -10 12 GeV and for effective two hierarchical right-handed neutrinos, leptogenesis takes place only in a narrower range of 5 × 10 10 -10 12 GeV. A multi-Higgs realization of this idea implies that there must be a pseudoscalar Higgs boson with mass less than 300 GeV. Generically, the vev alignment problem can be naturally avoided in our setting.

Mu-tau reflection symmetry with a texture-zero

“…This form for the neutrino mass matrix in the flavor basis (diagonal charged lepton masses) is known to predict maximal θ 23 = 45 • and δ = ±90 • at the same time that θ 13 = 0 is allowed [4][5][6]. Additionally, the Majorana phases are trivial and four discrete choices for the CP parities are possible [4][5][6]9]. These features lead to characteristic predictions for the neutrinoless double beta decay rate and leptogenesis [9].…”

“…These values for the neutrino parameters are still allowed by current global fits and in fact there are hints that δ ∼ −90 • [7,8]. The fixed values for the CP phases also lead to characteristic bands for the possible effective mass of neutrinoless double beta decay but still allows leptogenesis to occur if flavor effects are taken into account [9].…”

“…[9] that the simplest way of implementing CP µτ and guarantee diagonal charged lepton masses is to combine CP µτ with the combination L µ − L τ of family lepton numbers. This combination is trivial in the sense that these two symmetries commute and this feature allows us to avoid the vev alignment problem that requires special treatment in many models with discrete nonabelian flavor symmetries.…”

Consequences of minimal seesaw with complex μτ antisymmetry of neutrinos

“…We work in the basis in which charged leptons are mass diagonal. We are motivated by a flavor-based model constructed by Mohapatra and Nishi [42], which could accommodate a diagonal charged lepton mass matrix as well as a CP-transformed µτ interchange symmetry. Now we can relate U to the P M N S mixing matrix U P M N S : …”

“…Ref. [42] concluded that for the mass regime M 1 < 10 9 GeV, a resonant leptogenesis is only possible if one considers breaking in CP µτ , since in this regime the muon and tauon washout parameters are of equal strength. In our proposal of CP µτ A also, this conclusion is true.…”