Item

Abstract

Augmenting the Standard Model by three right-handed neutrinos allows for an anomaly-free gauge group extension G(max)=U(1)_{B - L} x U(1)_{L(e) - L(mu)} x U(1)_{L(mu) - L(tau)}. Simple U(1) subgroups of G(max) can be used to impose structure on the righthanded neutrino mass matrix, which then propagates to the active neutrino mass matrix via the seesaw mechanism. We show how this framework can be used to gauge the approximate lepton-number symmetries behind the normal, inverted, and quasidegenerate neutrino mass spectrum, and also how to generate texture-zeros and vanishing minors in the neutrino mass matrix, leading to testable relations among mixing parameters.