Interference bands in decays of doubly-charged Higgs bosons to dileptons in the minimal type-II seesaw model at the TeV scale

TL;DR

This paper studies how interference effects between light neutrinos and a heavy Majorana neutrino influence the decay patterns of doubly-charged Higgs bosons in a minimal type-II seesaw model at the TeV scale, revealing challenges in distinguishing models at the LHC.

Contribution

It introduces the concept of interference bands in decay branching ratios caused by light and heavy neutrinos in the minimal type-II seesaw model, highlighting their impact on collider phenomenology.

Findings

Interference bands for decay branching ratios are identified in the 10^{-8} to 10^{-5} range.

Heavy neutrino contributions significantly affect decay patterns of doubly-charged Higgs bosons.

Distinguishing the type-II seesaw model from the triplet seesaw model at the LHC is very challenging in the interference region.

Abstract

The dileptonic decays of doubly-charged Higgs bosons H^{\pm\pm} are investigated in the minimal type-II seesaw model with one Higgs triplet \Delta and one heavy Majorana neutrino N_1 at the TeV scale. We show that the branching ratios {\cal B}(H^{\pm\pm} \to l^\pm_\alpha l^\pm_\beta) depend not only on the mass and mixing parameters of three light neutrinos \nu_i (for i=1,2,3), but also on those of N_1. Assuming the mass of N_1 to lie in the range 200 GeV--1 TeV, we figure out the generous interference bands for the contributions of \nu_i and N_1 to {\cal B}(H^{\pm\pm} \to l^\pm_\alpha l^\pm_\beta): \sqrt{|\sin\theta_{i4} \sin\theta_{j4}|} \sim 10^{-8}--10^{-5}, where \theta_{i4} and \theta_{j4} measure the strength of charged-current interactions of N_1. We illustrate some salient features of the interference bands by considering three typical mass patterns of \nu_i, and stress that it is very difficult to distinguish the type-II seesaw model from the triplet seesaw model in such a parameter region at the Large Hadron Collider.