Description
Recently precise experiments have suggested that there is a discrepancy between theoretical and experimental values of muon g-2 based on the Standard Model (SM). It is known that the $$U(1)_{¥mu-¥tau}$$ gauge model can solve this. There are also studies that describe neutrino physics in terms of this symmetry-based model. For example, an analytical method has been proposed to give predictions for neutrino masses and Majorana phases that have not been experimentally determined based on models with $$U(1)_{¥mu-¥tau}$$ gauge symmetry and three right-handed neutrinos and a scalar field with $$U(1)_{¥mu-¥tau}$$ charge are added to the SM when the models have two zero components in the neutrino mass matrix and its inverse matrix (two zero texture or minor structure). The scalar fields added here take on different neutrino mass matrix structures for each behavior with respect to the $$SU(2)$$ gauge symmetry of the SM. The predictions obtained in the above analysis are subject to change as the neutrino oscillation experiments are refined and the experimental data are updated. We therefore performed the analysis using the latest data (NuFITv5.2) and confirmed the existence of a parameter region that is not excluded in the SM+right-handed neutrino + $$SU(2)$$ doublet scalar model, which was excluded in the previous study. On the other hand, focusing on the newly added $$U(1)_{¥mu-¥tau}$$ gauge symmetry, the simple SM+right-handed neutrino+ $$SU(2)$$ doublet scalar model is excluded due to Atomic Parity Violation, meson decay, and other limitations from cosmological observations. So the simple SM + right-handed neutrino + $$SU(2)$$ doublet scalar model is excluded. We therefore add a $$SU(2)$$ singlet scalar to this model which relaxes the restriction and found to allow us to place a limit on the ratio of the vacuum expectation values of the two types of scalar fields. This talk is based on the collaboration with Kento Asai, Shohei Okawa and Koji Tsumura.
