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T: Fachverband Teilchenphysik

T 87: Neutrinophysik (Theorie)

T 87.7: Vortrag

Mittwoch, 29. März 2017, 18:15–18:30, VSH 05

From CP Phases to Yukawa Textures - Maximal Yukawa Hierarchies in Minimal Seesaw Models — •Thomas Rink and Kai Schmitz — Max-Planck-Institut für Kernphysik, Heidelberg, Deutschland

The type-I seesaw mechanism involving only two right-handed neutrinos represents a minimal model to account for the observed masses and mixings in the Standard Model neutrino sector. It features four real parameters that cannot be fully fixed by the current data: two CP-violating phases, δ and σ, as well as one complex parameter, z, that is experimentally inaccessible at low energies. We perform a systematic scan over the complex z plane and study maximal hierarchies in the neutrino Yukawa matrix that are still consistent with observations for given values of δ and σ. Our analysis generalizes previous studies of so-called texture zeros in the neutrino Yukawa matrix and demonstrates that relaxing this assumption significantly enlarges the range of possible Yukawa matrices. Allowing for small corrections, models with an approximate two-zero texture can be realized even in the case of a normally ordered light-neutrino mass spectrum, which is usually ruled out in this framework. For the inverted hierarchy, we further show that small perturbations can resurrect Yukawa textures which were inconsistent with observations. Our analysis is based on a novel hierarchy parameter that allows us to assess to what extent any given Yukawa matrix exhibits a certain flavor texture. Generalization of this parameter paves the way for similar studies in other neutrino mass models.