Capability of future linear colliders to discover heavy neutral CP-even and CP-odd Higgs bosons within Type-I 2HDM

TL;DR

This paper evaluates the potential of future linear colliders to detect heavy neutral Higgs bosons in the Type-I 2HDM through specific decay channels, demonstrating promising observability at realistic luminosities.

Contribution

It introduces a detailed simulation study of heavy Higgs boson detection prospects at a 1 TeV linear collider within the Type-I 2HDM, focusing on leptonic and di-photon decay signatures.

Findings

Higgs bosons H and A are detectable with >5σ significance.

Detection is feasible at integrated luminosities of 111 and 201 fb^{-1}.

Results are applicable to future collider experiments.

Abstract

In this study, assuming the type-I 2HDM at SM-like scenario, observability of heavy neutral CP-even and CP-odd Higgs bosons $H$ and $A$ at a linear collider operating at $\sqrt{s}=1$ TeV is investigated through the signal process chain $e^- e^+ \rightarrow A H \rightarrow ZHH$ where the $Z$ boson experiences a leptonic ($e^-e^+$ or $\mu^-\mu^+$) decay and the $H$ Higgs boson is assumed to decay into a di-photon. This signal process is motivated especially by the clean signature which leptonic and photonic events can provide at colliders, and also by the enhancement due to the charged Higgs-mediated contribution to $H$ di-photon decay at large $\tan\beta$ values. Simulation is based on four benchmark points according to which the Higgs mass $m_H$ ($m_A$) varies within the range $150$-$300$ ($200$-$400$) GeV. Energy smearing of jets and photons are performed, and momentum smearing is also applied to leptons. Results indicate that, for all of the assumed benchmark points, the Higgs bosons $H$ and $A$ are observable with measurable masses, and with signals exceeding $5\sigma$ at integrated luminosities $111$ and $201\,fb^{-1}$ respectively. Such luminosities are easily accessible to future linear colliders.