Radiative origin of neutrino masses

Mechanisms for Majorana neutrino mass generation can be classified according to the level at which the Weinberg operator is generated. The different possibilities can be sorted in “canonical” tree-level and loop-induced realizations, the latter being motivated by their potential experimental testability. Here, we discuss the one- and two-loop cases, paying special attention to systematic classification schemes, whose aim is that of constructing a full picture for neutrino mass generation