AbstractIn 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 $$v_\Delta $$
v
Δ
ranging from $$1.5\times 10^{-9}~\text {GeV}$$
1.5
×
10
-
9
GeV
to $$1.3~\text {GeV}$$
1.3
GeV
and the mass splitting $$\Delta m$$
Δ
m
between the nearby states of the Higgs quadruplet satisfying $$|\Delta m|\lesssim 30~\text {GeV}$$
|
Δ
m
|
≲
30
GeV
. About $$100~\text {fb}^{-1}$$
100
fb
-
1
of data are required at most for $$5\sigma $$
5
σ
discovery. We also revisit the sensitivity at the Large Hadron Collider (LHC) and find that $$5\sigma $$
5
σ
discovery of the triply charged Higgs boson below 1 TeV can be reached for a relatively small $$v_\Delta $$
v
Δ
. For example, if $$v_\Delta =10^{-6}~\text {GeV}$$
v
Δ
=
10
-
6
GeV
and $$\Delta m=0$$
Δ
m
=
0
, the integrated luminosity of $$330~\text {fb}^{-1}$$
330
fb
-
1
is needed. But for a relatively large $$v_\Delta $$
v
Δ
, i.e., $$v_\Delta \gtrsim 10^{-3}~\text {GeV}$$
v
Δ
≳
10
-
3
GeV
, the triply charged Higgs boson above about 800 GeV cannot be discovered even in the high-luminosity LHC era. For $$\Delta m>0$$
Δ
m
>
0
, the cascade decays are open and the sensitivity can be improved depending on the value of $$v_\Delta $$
v
Δ
.