Compatibility of θ 13 and the Type I seesaw model with A 4 symmetry

Abstract

We derive formulae for neutrino masses and mixing angles in a type I seesaw framework with an underlying A 4 flavor symmetry. In particular, the Majorana neutrino mass matrix includes contributions from an A 4 triplet, 1, 1 ′ , and 1 ′′ flavon fields. Using these formulae, we constrain the general A 4 parameter space using the updated global fits on neutrino mixing angles and mass squared differences, including results from the Daya Bay and RENO experiments, and we find predictive relations among the mixing parameters for certain choices of the triplet vacuum expectation value. In the normal hierarchy case, sizable deviation from maximal atmospheric mixing is predicted, and such deviation is strongly correlated with the value of θ 13 in the range of ∼ (8 − 10) • . On the other hand, such deviation is negligible and insensitive to θ 13 in the inverted mass hierarchy case. We also show expectations for the Dirac CP phase resulting from the parameter scan. Future refined measurements of neutrino mixing angles will test these predicted correlations and potentially show evidence for particular triplet vev patterns.

Large θ 13 in a SUSY SU(5) × T′ model

“…one singlet flavon fields of the original A 4 models, it has also been shown [26] that the inclusion of additional A 4 singlets can also give sizable deviation from the TBM predictions, leading to phenomenologically viable predictions.…”

“…In light of the discovery of a large θ 13 , various models based on discrete family symmetries, such as A 4 [24][25][26][27], S 4 [28], T [29] and A 5 [30] have been revisited lately, and more examples can be found in the review [31]. It has been pointed out [32] [7].…”

Radiative corrections to the leptonic DiracCP-violating phase

“…For instance, it has been shown in Ref. [9] that δ ≈ 2π/3 (or 4π/3) and δ ≈ π/3 (or 5π/3) for different breaking patterns of the A 4 flavor symmetry in the type-I seesaw model, where three heavy right-handed neutrino singlets are introduced to realize the dimension-five Weinberg operator. If the vacuum alignment problem is further solved in the framework of supersymmetry, significant radiative corrections to these theoretical predictions of δ could be possible.…”

“…[13] phenomenological assumptions have recently been proposed to describe the observed leptonic mixing pattern, in particular a relatively large θ 13 . Interestingly, the leptonic CP-violating phase δ has been predicted in some models to be rather large (e.g., δ > π/3) or even maximal (i.e., δ = π/2) [8,9]. In other models, leptonic CP violation is shown to be absent, namely δ = 0 or π [10].…”

Common origin of nonzero θ13 and baryon asymmetry of the Universe in a TeV scale seesaw model with A4 flavor symmetry

“…Such corrections can originate from the charged lepton sector or the neutrino sector itself like for example, in the form of a new contribution to the neutrino mass matrix. This has led to several works including [19][20][21][22][23][24][25][26] within different BSM frameworks.…”