Production of charged Higgs bosons associated with CP-even Higgs bosons at future multi--TeV muon colliders

Abstract

We report the first results for charged Higgs boson production associated with CP-even Higgses at future multi--TeV muon colliders within the scenario of the Type-Y Two-Higgs-Doublet Model (THDM). The valid parameter regions in the Type-Y THDM are first updated, and based on the allowed parameter space, all two-body decay channels of the charged Higgs boson are then computed with the help of {\tt H-COUP}. Both production processes $μ^- μ^+ \to H^\pm H^\mp h, H^\pm H^\mp H \to t\bar{t} b\bar{b} h, t\bar{t} b\bar{b}H$ are scanned over the constrained parameter space of the considered model. The production cross sections can reach $\sim 0.5$ fb in several regions of the parameter space. The results provide an opportunity to probe charged Higgs bosons produced in association with the heavy CP-even Higgses at the high integrated luminosities proposed for future multi--TeV muon colliders. Furthermore, we evaluate the signal significances for $μ^- μ^+ \to H^\pm H^\mp h \to t\bar{t} b\bar{b} h \to t\bar{t} b\bar{b} b\bar{b}$ with respect to the Standard Model backgrounds. We also estimate the significances by including the top quark decay into leptons and bottom quarks and considering $b$-tagging. Thanks to the high integrated luminosities anticipated at future multi--TeV muon colliders,we find that the signal significances can exceed $\sim 3σ$ at several benchmark points selected in the viable parameter space of the Type-Y THDM.

Figures (9)

• Figure 1: The scatter plots show the correlations among $m_A$, $m_{H^\pm}$, and $m_H$ in the upper-left panel, and those among $m_A$, $m_{H^\pm}$, and $m_H - m_A$ in the upper-right panel. The lower-left plot shows the correlations between $m_{12}^2$, $m_{H^\pm}$, and $\tan\beta$, while the lower-right panel illustrates the correlations among $m_{12}^2$, $m_H$, and $\tan\beta$.
• Figure 2: The upper-left plot displays the branching fractions of the charged Higgs for all decay channels at the benchmark frist point presented in Table \ref{['BP']}. The upper-right plot shows the decay rate of $H^\pm \to tb$, while the lower-left plot corresponds to $H^\pm \to W^\pm h$. The lower-right plot illustrates $H^\pm \to W^\pm H$. All plots are generated as functions of the charged Higgs mass and $t_{\beta}$.
• Figure 3: The upper-left plot shows for the branching fractions of the charged Higgs boson for the decay $H^\pm \to W^\pm A$, and the upper-right plot shows the decay rate of $H^\pm \to \tau \nu_{\tau}$. Meanwhile, the lower-left plot corresponds to $H^\pm \to W^\pm Z$ and the lower-right plot illustrates $H^\pm \to W^\pm \gamma$. It is noted that all plots are generated as functions of the charged Higgs mass and $t_{\beta}$.
• Figure 4: The production cross sections for $\mu^-\mu^+ \to H^\pm H^\mp h \to t\bar{t} b \bar{b} h$ at $\sqrt{s} = 3$ TeV (left) and $\sqrt{s} = 5$ TeV (right) are shown in the parameter space of $m_{H^\pm}$ and $t_{\beta}$ (upper plots), $m_{H^\pm}$ and $m_H$ (middle plots), and $m_{H^\pm}$ and $m_A - m_H$ (lower plots).
• Figure 5: The production cross sections for $\mu^-\mu^+ \to H^\pm H^\mp H \to t\bar{t} b \bar{b} H$ at $\sqrt{s} = 3$ TeV (left) and $\sqrt{s} = 5$ TeV (right) are shown in the parameter space of $m_{H^\pm}$ and $t_{\beta}$ (upper plots), $m_{H^\pm}$ and $m_H$ (middle plots), and $m_{H^\pm}$ and $m_A - m_H$ (lower plots).