Generating phenomenologically viable neutrino masses within SU(5)

Determine mechanisms and model structures within SU(5) grand unification that generate phenomenologically viable neutrino masses, given that the Georgi–Glashow SU(5) model preserves a global U(1)_{B−L} symmetry and leaves neutrinos massless.

Background

The Georgi–Glashow SU(5) model unifies quarks and leptons and the Standard Model gauge interactions but preserves a global U(1)_{B−L} symmetry, which forbids Majorana masses and leaves neutrinos massless. Consequently, explaining observed neutrino masses requires extending SU(5) in a way that breaks lepton number by two units.

This paper explores how such extensions that generate Majorana neutrino masses in SU(5) inherently induce |ΔB|=2 interactions, connecting neutrino mass generation to neutron–antineutron oscillation. However, the general challenge of identifying SU(5)-consistent mechanisms that yield phenomenologically viable neutrino masses is explicitly highlighted as an open problem.