Direct determination of neutrino mass parameters at future colliders

TL;DR

This paper explores how future collider experiments can determine neutrino mass parameters in the triplet Higgs seesaw model by measuring specific Higgs decay branching ratios, providing insights beyond neutrino oscillation data.

Contribution

It demonstrates that measuring doubly charged Higgs decay patterns at colliders can reveal neutrino mass details not accessible through oscillation experiments, specifically in the triplet Higgs seesaw scenario.

Findings

Collider measurements can determine neutrino mass hierarchy.

Branching ratios reveal Majorana phases.

Potential to measure lightest neutrino mass.

Abstract

If the observed light neutrino masses are induced by their Yukawa couplings to singlet right-handed neutrinos, natural smallness of those renders direct collider tests of the electroweak scale neutrino mass mechanisms almost impossible both in the case of Dirac and Majorana (seesaw of type I) neutrinos. However, in the triplet Higgs seesaw scenario the smallness of light neutrino masses may come from the smallness of B-L breaking parameters, allowing sizable Yukawa couplings even for a TeV scale triplet. We show that, in this scenario, measuring the branching fractions of doubly charged Higgs to different same-charged lepton flavours at LHC and/or ILC experiments will allow one to measure the neutrino mass parameters which neutrino oscillation experiments are insensitive to, including the neutrino mass hierarchy, lightest neutrino mass and Majorana phases.