Same-sign tetralepton signature in type-II seesaw at lepton colliders * *Supported by the National Natural Science Foundation of China (11605074, 11805081), Natural Science Foundation of Shandong Province (ZR2019QA021, ZR2018MA047), Joint Large-Scale Scientific Facility Funds of the NSFC and CAS (U1732263, U2032115)

Xu-Hong Bai,Zhao-Xia Meng,Hong-Lei Li,Yi Jin,Zhi-Long Han

doi:10.1088/1674-1137/ac2ed1

Abstract

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 . In this study, we investigate this signature at future lepton colliders, such as the ILC, CLIC, and MuC. Direct searches for doubly charged scalar at the LHC have excluded GeV in the decay mode. Therefore, we choose GeV as our benchmark scenarios. Constrained by direct search, is the only viable decay mode for GeV at the TeV ILC. With an integrated luminosity , the promising region, with approximately 150 signal events, corresponds to a narrow band in the range of GeV. Meanwhile, for GeV at the TeV CLIC, approximately 10 signal events can be produced with . For heavier triplet scalars GeV, although the decay mode is allowed, the cascade decays are suppressed. A maximum event number can be obtained at approximately GeV and for GeV with at the TeV CLIC. Finally, we find that this signature is not promising for GeV at the TeV MuC. Based on the benchmark scenarios, we also study the observability of this signature. In the mode, one can probe GeV at future lepton colliders.

Highlights

The discovery of neutrino oscillations [1,2,3] confirms that neutrinos have sub-eV masses
We study the novel same-sign tetra-lepton signature in type-II seesaw at the future lepton colliders
The signature arises from the mixing of associated production of Higgs fields H0A0 followed by the cascade decays H0/A0 → H±W ∗, H± → H±±W ∗, and H±± → ± ±/W ±W ± with W ± → ±ν

Summary

INTRODUCTION

The discovery of neutrino oscillations [1,2,3] confirms that neutrinos have sub-eV masses. There are three possible ways at tree level to realize this operator [5], which correspond to the canonical type-I [6, 7], type-II [8,9,10,11], and type-III [12] seesaw To verify whether these scenarios are realized in nature, the signatures of seesaw models at colliders have been extensively studied [13,14,15]. Among various possible collider signatures of the type-II seesaw, a unique one is the same-sign tetralepton signature [42, 43], which arises from the mixing of neutral Higgs bosons and their cascade decays to singly and doubly charged Higgs bosons.

THE MODEL

SAME-SIGN TETALEPTON SIGNATURE

TeV ILC 3 TeV CLIC 6 TeV MuC 14 TeV LHC 100 TeV FCC-hh

CONCLUSION