Triply charged Higgs bosons at a 100 TeV pp collider

In this work, we study the potential of searching for triply charged Higgs boson originating from a complex Higgs quadruplet in the final state with at least three same-sign leptons. A detailed collider analysis of the SM backgrounds and signals is performed at a 100 TeV pp collider for the triply charged Higgs boson mass below 1 TeV and the Higgs quadruplet vacuum expectation value $$v_\Delta $$ ranging from $$1.5\times 10^{-9}~\text {GeV}$$ to $$1.3~\text {GeV}$$ and the mass splitting $$\Delta m$$ between the nearby states of the Higgs quadruplet satisfying $$|\Delta m|\lesssim 30~\text {GeV}$$ . About $$100~\text {fb}^{-1}$$ of data are required at most for $$5\sigma $$ discovery. We also revisit the sensitivity at the Large Hadron Collider (LHC) and find that $$5\sigma $$ discovery of the triply charged Higgs boson below 1 TeV can be reached for a relatively small $$v_\Delta $$ . For example, if $$v_\Delta =10^{-6}~\text {GeV}$$ and $$\Delta m=0$$ , the integrated luminosity of $$330~\text {fb}^{-1}$$ is needed. But for a relatively large $$v_\Delta $$ , i.e., $$v_\Delta \gtrsim 10^{-3}~\text {GeV}$$ , the triply charged Higgs boson above about 800 GeV cannot be discovered even in the high-luminosity LHC era. For $$\Delta m>0$$ , the cascade decays are open and the sensitivity can be improved depending on the value of $$v_\Delta $$ .