Same-sign tetralepton signature in type-Ⅱ seesaw at lepton colliders

The same-sign tetralepton signature via the mixing of neutral Higgs bosons and their cascade decays to charged Higgs bosons is a unique signal in the type-Ⅱ seesaw model with the mass spectrum M_A⁰≈M_H⁰>M_H⁺>M_H^±±.In this study,we investigate this signature at future lepton colliders,such as the ILC,CLIC,and MuC.Direct searches for doubly charged scalar H^±±at the LHC have excluded MHg+t<350(870) GeV in the H^±±+W^±W(±)(l^±±)decay mode.Therefore,we choose M_A⁰=400,600,1000,1500 GeV as our benchmark scenarios.Constrained by direct search,H^±±+W^±W(±)(l^±±)d=is the only viable decay mode for Mρ=400 GeV at the √s=1 TeV ILC.With an integrated luminosity L=8 ab^-1,the promising region,with approximately 150 signal events,corresponds to a narrow band in the range of 10^-4 GeV≤v△≤10^-2GeV.Meanwhile,for Mpo=600 GeV at the √s=1.5 TeV CLIC,approximately 10 signal events can be produced with L=2.5 ab^-1.For heavier triplet scalars M_A⁰■870 GeV,although the H^±± decay mode is allowed,the cascade decays are suppressed.A maximum event number~16 can be obtained at approximately v△~4×10⁴GeV and λ₁₄~0.26 for M_A⁰=1000 GeV with L=5 ab^-1 at the √s=3 TeV CLIC.Finally,we find that this signature is not promising for M_A⁰= 1500 GeV at the √s=6 TeV MuC.Based on the benchmark scenarios,we also study the observability of this signature.In the H^±±+W^±W(±)(l^±±)d mode,one can probe MρS 800(1160) GeV at future lepton colliders.

Same-sign tetralepton signature in type-II seesaw at lepton colliders

The same-sign tetralepton signature via the mixing of neutral Higgs bosons and their cascade decays to charged Higgs bosons is a unique signal in the type-II seesaw model with the mass spectrum begin{document}$M_{A^0}simeq M_{H^0}>M_{H^pm}>M_{H^{pmpm}}$end{document}. In this study, we investigate this signature at future lepton colliders, such as the ILC, CLIC, and MuC. Direct searches for doubly charged scalar begin{document}$H^{pmpm}$end{document} at the LHC have excluded begin{document}$M_{H^{pmpm}}<350(870)$end{document} GeV in the begin{document}$H^{pmpm}to W^pm W^pm (ell^pmell^pm)$end{document} decay mode. Therefore, we choose begin{document}$M_{A^0}=400,600,1000,1500$end{document} GeV as our benchmark scenarios. Constrained by direct search, begin{document}$H^{pmpm}to W^pm W^pm$end{document} is the only viable decay mode for begin{document}$M_{A^0}=400$end{document} GeV at the begin{document}$sqrt{s}=1$end{document} TeV ILC. With an integrated luminosity begin{document}$mathcal{L}=8~ mathrm{ab}^{-1}$end{document}, the promising region, with approximately 150 signal events, corresponds to a narrow band in the range of begin{document}$10^{-4}~text{GeV}lesssim v_Delta lesssim10^{-2}$end{document} GeV. Meanwhile, for begin{document}$M_{A^0}=600$end{document} GeV at the begin{document}$sqrt{s}=1.5$end{document} TeV CLIC, approximately 10 signal events can be produced with begin{document}$mathcal{L}=2.5~text{ab}^{-1}$end{document}. For heavier triplet scalars begin{document}$M_{A^0}gtrsim 870$end{document} GeV, although the begin{document}$H^{pmpm}to ell^pm ell^pm$end{document} decay mode is allowed, the cascade decays are suppressed. A maximum event number begin{document}$sim 16$end{document} can be obtained at approximately begin{document}$v_Deltasim4times10^{-4}$end{document} GeV and begin{document}$lambda_4sim0.26$end{document} for begin{document}$M_{A^0}=1000$end{document} GeV with begin{document}$mathcal{L}=5~ mathrm{ab}^{-1}$end{document} at the begin{document}$sqrt{s}=3$end{document} TeV CLIC. Finally, we find that this signature is not promising for begin{document}$M_{A^0}=1500$end{document} GeV at the begin{document}$sqrt{s}=6$end{document} TeV MuC. Based on the benchmark scenarios, we also study the observability of this signature. In the begin{document}$H^{pmpm}to W^pm W^pm(ell^pmell^pm)$end{document} mode, one can probe begin{document}$M_{A^0}lesssim800(1160)$end{document} GeV at future lepton colliders.