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A predictive framework for fermion masses and mixing is given by the supersymmetric SO (10) model with one 10₇, one 126₇, one 126₇, and one 210₇ Higgs representations, and type-II seesaw dominating the neutrino mass matrix. We investigate the origin of the tension between this model and lepton mixing data and refine previous numerical analyses. We discuss an extension of the minimal model that includes one 120₇ chiral superfield representation. This exhausts the possible renormalizable contributions to the Yukawa sector. In spite of the increase in the number of parameters the predictivity of the minimal setting is not spoiled. We argue that the contributions to fermion masses due to the doublet components of 120₇ can be naturally small compared to those of 10₇ and 126₇, thus acting as a perturbation in the fermion mass generation. The antisymmetric nature of the 120₇ Yukawa coupling affects at leading order the determination of the mixing angles and it allows to remove the inconsistencies between predictions and data on the neutrino parameters. An improvement in the experimental bound on U₄₃ can tell this scenario from the minimal model.
Bertolini et al. (Tue,) studied this question.