We study the seesaw realization of a A4 model with two Higgs singlets. In this model, the mixing angle θ13 and leptogenesis are zero if the components of right handed neutrino mass matrix resulting from the two Higgs singlets are exact degenerate. We then study the minimal breaking of the model by a tiny shift between aforementioned components. This minimal breaking results in deviations of lepton mixing angles from their tri-bimaximal mixing values in which the current experimental value of θ13 can be achieved. Besides, the baryon asymmetry of the Universe is successfully generated through non-zero leptogenesis by the decay of right handed neutrinos. | Communications in Physics, Vol. 24, No. 2 (2014), pp. 113-123 TWO HIGGS SINGLETS A4 FLAVOR SYMMETRY WITH MINIMAL BREAKING NGUYEN THANH PHONG Department of Physics, Can Tho University, Can Tho city, Vietnam E-mail: thanhphong@ Received 24 April 2014 Accepted for publication 22 June 2014 Abstract. We study the seesaw realization of a A4 model with two Higgs singlets. In this model, the mixing angle θ13 and leptogenesis are zero if the components of right handed neutrino mass matrix resulting from the two Higgs singlets are exact degenerate. We then study the minimal breaking of the model by a tiny shift between aforementioned components. This minimal breaking results in deviations of lepton mixing angles from their tri-bimaximal mixing values in which the current experimental value of θ13 can be achieved. Besides, the baryon asymmetry of the Universe is successfully generated through non-zero leptogenesis by the decay of right handed neutrinos. Keywords: A4 model, leptogenesis, seesaw mechanism I. INTRODUCTION The evidence of neutrino oscillations absolutely confirmed neutrino has mass and they are mixing. Based on neutrino experimental data, in 2002, P. F. Harrison et al. [1] proposed the structure of lepton mixing matrix which named Tri-Bimaximal (TB). According to this structure, the reactor mixing angle, θ13 , is zero and the Dirac CP violating phase is meaningless. Subsequently, there were a lot of efforts to find a natural model that leads to TB mixing pattern of leptons, and a fascinating way seems to be the use of some discrete non-Abelian flavor groups added to the gauge groups of the Standard Model (SM). There is a series of models based on the symmetry group A4 [2, 3], T ′ [4], and S4 [5]. The common feature of these models is that they are realized at very high energy scale Λ and the groups are spontaneously broken due by a set of scalar multiplets. Based on the latest results of T2K [6], MINOS [7], RENO [8], Double CHOOZ [9] and Daya Bay .
