Neutrino mass with large $SU(2)_L$ multiplet fields

TL;DR

This paper introduces large $SU(2)_L$ multiplet fields in the standard model to generate neutrino masses, predicts collider signatures, and discusses their detectability at the LHC.

Contribution

It proposes a novel extension with large multiplets that naturally suppress neutrino masses and relax Yukawa hierarchies, with analysis of collider phenomenology.

Findings

Neutrino masses are generated via small VEVs and inverse fermion masses.

Specific collider signatures due to custodial symmetry violation are identified.

Potential detectability of charged multiplet particles at the LHC is discussed.

Abstract

We propose an extension of the standard model introducing large $SU(2)_L$ multiplet fields which are quartet and septet scalars and quintet Majorana fermions. These multiplets can induce the neutrino masses via interactions with the $SU(2)$ doublet leptons. We then find the neutrino masses are suppressed by small vacuum expectation value of the quartet/septet and an inverse of quintet fermion mass relaxing the Yukawa hierarchies among the standard model fermions. We also discuss collider physics at the Large Hadron Collider considering production of charged particles in these multiplets, and due to effects of violating custodial symmetry, some specific signatures can be found. Then we discuss the detectability of these signals.