Probing Doubly Charged Higgs Bosons with Three-Body Associated Production at Future $e^+e^-$ Colliders

TL;DR

This paper investigates the potential to discover doubly charged Higgs bosons at future electron-positron colliders through three-body production channels, showing these modes can outperform traditional pair-production in certain parameter regions.

Contribution

It introduces and analyzes three-body associated production modes for doubly charged Higgs bosons, demonstrating their significance and discovery potential at future colliders, which is a novel approach compared to conventional methods.

Findings

Three-body production modes can exceed pair-production rates.

Cross-sections reach up to 100 fb at 500-1500 GeV.

Discovery is feasible with high luminosity and energies.

Abstract

We study the discovery prospects for a doubly charged Higgs boson $H^{\pm\pm}$ in the 2-Higgs Doublet Model with type-II seesaw (2HDMcT) at future $e^+e^-$ colliders. Focusing on the three-body channels $e^+e^- \to H^{\pm\pm}H_1^{\mp}H_1^{\mp}$ and $e^+e^- \to H^{\pm\pm}H_1^{\mp}W^{\mp}$, we scan the model parameter space subject to theoretical consistency as well as current collider, flavor and Electro-Weak Precision Observables (EWPOs). We find that these $2\to3$ production modes can exceed the conventional pair-production rate $e^+e^- \to H^{++}H^{--}$, followed by $H^{\pm\pm}\to H_1^{\pm}H_1^{\pm}$ and $H^{\pm}_1W^{\pm}$ decays, over wide regions, particularly above the $H^{\pm\pm}\to H_1^{\pm}H_1^{\pm}$ and $H^{\pm\pm}\to H_1^{\pm}W^{\pm}$ thresholds, reaching cross-sections up to ${\cal O}(10^2)$~fb for $\sqrt{s}=500$--$1500$~GeV. A detector-level analysis of the $4\ell + E_T^{\text{miss}}$ signature, including dominant multiboson and top quark backgrounds, shows that discovery sensitivity is achievable for $\sqrt{s}=1000$-$1500$~GeV with integrated luminosities in the few ab$^{-1}$ range, even in the presence of realistic systematic uncertainties.