Revisiting the A4 model for leptons in light of NuFIT 3.2. (14th August 2018)

• Record Type: Journal Article
• Authors: Kang, Sin Kyu; Shimizu, Yusuke; Takagi, Kenta; Takahashi, Shunya; Tanimoto, Morimitsu
• Is Part Of: Progress of theoretical and experimental physics. Volume 2018:Number 8(2018)
• Publication Date: 2018-08-14
• Subjects: B40 -- B52 -- B54; Physics -- Periodicals; Mathematical physics -- Periodicals; 530.05
• DOI: 10.1093/ptep/pty080
• Languages: English
• ISSNs: 2050-3911

Abstract

Abstract: We revisit the $A_4$ model for leptons in light of the new result of NuFIT 3.2. We introduce a new flavon $\eta$ transforming as an $A_4$ singlet $1'$ or $1''$, which couples to both charged leptons and neutrinos in next-to-leading-order operators. The model consists of five parameters: the lightest neutrino mass $m_1$, the vacuum expectation value of $\eta$, and three CP-violating phases after inputting the experimental values of $\Delta m_{\rm atm}^2$ and $\Delta m_{\rm sol}^2$ . The model with the $1''$ singlet flavon gives the prediction of $\sin^2 \theta_{12}$ around the best fit of NuFIT 3.2 while staying near the maximal mixing of $\theta_{23}$ . Inputting the experimental mixing angles with the $1\, \sigma$ error-bar, the Dirac CP-violating phase is clearly predicted to be $|\delta_\text{CP}|=50$ –$120^\circ$, which will be tested by the precise observed value in the future. In order to get the best-fit value $\sin^2\theta_{23}=0.538$, the sum of three neutrino masses is predicted to be larger than $90$ meV. The cosmological observation for the sum of the neutrino masses will also provide a crucial test of our predictions. It is remarked that the model is consistent with the experimental data only for the normal hierarchy of neutrino masses.