Neutrino Mass and Mixing in the Seesaw Playground

Abstract

We discuss neutrino mass and mixing in the framework of the classic seesaw mechanism, involving right-handed neutrinos with large Majorana masses, which provides an appealing way to understand the smallness of neutrino masses. However, with many input parameters, the seesaw mechanism is in general not predictive. We focus on natural implementations of the seesaw mechanism, in which large cancellations do not occur, where one of the right handed neutrinos is dominantly responsible for the atmospheric neutrino mass, while a second right-handed neutrino accounts for the solar neutrino mass, leading to an effective two right-handed neutrino model. We discuss recent attempts to predict lepton mixing and CP violation within such natural frameworks, focussing on the Littlest Seesaw and its distinctive predictions.

12 pages, 5 figures, Invited contribution to the Special Issue on Neutrino Oscillation in order to celebrate the Nobel Prize in Physics 2015 - for publication in Nuclear Physics B

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• Common origin of ${\theta }_{13}$ and dark matter within the flavor symmetric scoto-seesaw framework
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• Do we understand the internal spaces of second quantized fermion and boson fields, with gravity included? Relation with strings theories
• Proceedings to the 27th Workshop "What Comes Beyond the Standard Models" Bled, July 8-17, 2024
• A Hybrid Type I + III Inverse Seesaw Mechanism in $U(1{)}_{R-L}$-symmetric MSSM