Neutrino Masses and Mixings from String Theory Instantons

Understand

We study possible patterns of neutrino masses and mixings in string models in which Majorana neutrino masses are generated by a certain class of string theory instantons recently considered in the literature.

• These instantons may generate either directly the dim=5 Weinberg operator or right-handed neutrino Majorana masses, both with a certain flavour-factorised form.
• A hierarchy of neutrino masses naturally appears from the exponentially suppressed contributions of different instantons.
• The flavour structure is controlled by string amplitudes involving neutrino fields and charged instanton zero modes.