Mechanism responsible for neutrino masses

Determine the mechanism responsible for generating nonzero neutrino masses, distinguishing among possibilities such as predominantly Dirac masses via Yukawa couplings and Majorana masses via the Weinberg operator and seesaw scenarios, using experimental and observational evidence.

Background

Neutrino oscillation measurements over more than two decades have precisely determined the parameters governing flavor transitions, yet they do not reveal how neutrinos acquire mass. Competing frameworks include Majorana masses, often associated with high-scale seesaw mechanisms testable via neutrinoless double-beta decay, and Dirac masses requiring tiny Yukawa couplings and potentially leading to quasi-Dirac phenomenology.

Astrophysical neutrino observations, especially over cosmic baselines and across wide energies, can provide complementary evidence to laboratory experiments to help pinpoint the correct mass-generation mechanism.