TeV-scale Type-II Seesaw Models and Possible Collider Signatures

TL;DR

This paper explores TeV-scale Type-II seesaw models with flavor symmetries, proposing scenarios that explain neutrino masses and mixing, and discusses potential collider and neutrino experiment signatures for testing these models.

Contribution

It introduces three simple TeV-scale Type-II seesaw scenarios with broken flavor symmetries, linking neutrino properties to testable collider and oscillation experiment signatures.

Findings

Light neutrinos can be exactly massless under specific mass matrix conditions.

Proposes collider signatures involving lepton number violation and doubly-charged Higgs particles.

Discusses unitarity violation effects in neutrino oscillation experiments.

Abstract

A natural extension of the standard model to accommodate massive neutrinos is to introduce one Higgs triplet and three right-handed Majorana neutrinos, leading to a 6 \times6 neutrino mass matrix. We show that three light Majorana neutrinos (i.e., the mass eigenstates of \nu_e, \nu_\mu and \nu_\tau) are exactly massless, if and only if M_L = M_D M^{-1}_R M^T_D exactly holds in this seesaw model. We propose three simple Type-II seesaw scenarios with broken A_4 \times U(1)_X flavor symmetry to interpret the observed neutrino mass spectrum and neutrino mixing pattern. Such a TeV-scale neutrino model can be tested in two complementary ways: (1) searching for possible collider signatures of lepton number violation induced by the right-handed Majorana neutrinos and doubly-charged Higgs particles; and (2) searching for possible consequences of unitarity violation of the 3\times 3 neutrino mixing matrix in the future long-baseline neutrino oscillation experiments.