Discovery prospects for the 150 GeV charged scalar at future e⁺e⁻ colliders

The Real Higgs Triplet model, known as the Δ SM, is a minimal extension of the Standard Model (SM) obtained by adding a hypercharge 0 triplet ( Δ ). This simple model is motivated by the multi-lepton anomalies and excesses in di-photon, Zγ Z γ , and WW spectra at ≈ 152 ≈ 152 GeV. The model contains, in addition to the SM particle content, a CP -even neutral Higgs ( ⁰ Δ 0 ) and a charged state ( ^± Δ ± ), which are quasi-degenerate in mass. Observing the charged scalar at the LHC and measuring its mass is very challenging, since it dominantly decays to WZ , tb , and τ ν τ ν . In this article, we consider the discovery prospects of the charged Higgs with mass 150 GeV at future electron-positron colliders. Taking into account e⁺e⁻ → γ ^*,Z^* → ^± ^∓ e + e - → γ ∗ , Z ∗ → Δ ± Δ ∓ as the production mechanism and the dominant decay modes, we define three signal regions (SR) to study the 150 GeV charged Higgs properties: SR1: ≥ 3j + 1 ≥ 3 j + 1 ℓ , SR2: ≥ 3 + τ had ≥ 3 ℓ + τ had , SR3: ≥ 4j + τ had ≥ 4 j + τ had . For m^±=150\,GeV m Δ ± = 150 GeV , a <j