### References & Citations

# High Energy Physics - Theory

# Title: Majorana neutrino masses by D-brane instanton effects in magnetized orbifold models

(Submitted on 12 Mar 2021)

Abstract: We study Majorana neutrino masses induced by D-brane instanton effects in magnetized orbifold models. We classify possible cases, where neutrino masses can be induced. Three and four generations are favored in order to generate neutrino masses by D-brane instantons. Explicit mass matrices have specific features. Their diagonalizing matrices correspond to the bimaximal mixing matrix in the case with even magnetic fluxes, independently of the modulus value $\tau$. On the other hand, for odd magnetic fluxes, diagonalizing matrices correspond nearly to the tri-bimaximal mixing matrix near $\tau =i$, while they become the bimaximal mixing matrix for larger ${\rm Im}\tau$. For even fluxes, neutrino masses are modular forms of the weight 1 on $T^2/\mathbb{Z}_2$, and they have symmetries such as $S_4'$ and ${\Delta'}(96)\times \mathbb{Z}_3$.

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