Electroweak Breaking and Higgs Boson Profile in the Simplest Linear Seesaw Model

TL;DR

This paper explores a minimal linear seesaw model that extends the Standard Model with additional scalars, analyzing Higgs boson properties, neutrino mass generation, and potential invisible decays into majorons, with implications for astrophysics and collider experiments.

Contribution

It introduces a simple linear seesaw framework with a unique scalar sector, detailing Higgs and neutrino phenomenology, including invisible decay channels and astrophysical constraints.

Findings

Higgs boson can have significant invisible decay into majorons.

The model predicts a compressed scalar spectrum compatible with electroweak symmetry breaking.

Astrophysical constraints limit the properties of the majoron and scalar sector.

Abstract

We examine the simplest realization of the linear seesaw mechanism within the Standard Model gauge structure. Besides the standard scalar doublet, there are two lepton-number-carrying scalars, a nearly inert SU2 doublet and a singlet. Neutrino masses result from the spontaneous violation of lepton number, implying the existence of a Nambu-Goldstone boson. Such "majoron" would be copiously produced in stars, leading to stringent astrophysical constraints. We study the profile of the Higgs bosons in this model, including their effective couplings to the vector bosons and their invisible decay branching ratios. A consistent electroweak symmetry breaking pattern emerges with a compressed spectrum of scalars in which the "Standard Model" Higgs boson can have a sizeable invisible decay into the invisible majorons.