Light neutrinos from massless texture and below TeV seesaw scale

Understand

We present general conditions on Dirac and Majorana mass terms under which a type-I seesaw mechanism can lead to three exactly massless neutrinos at the tree level.

• We depict several examples where the conditions are satisfied and relate some of them to an underlying U(1) symmetry.
• We show that higher order corrections may generate the small observed masses and this may be achieved even when the heavy Majorana neutrinos are at the electroweak scale or a little higher.