Physics Letters B 767 (2017) 443–449
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Search for a light-charged Higgs in a two-Higgs-doublet type II seesaw
model at the LHC
Chuan-Hung Chen
a
, Takaaki Nomura
b,∗
a
Department of Physics, National Cheng-Kung University, Tainan 70101, Taiwan
b
School of Physics, KIAS, Seoul 130-722, Republic of Korea
a r t i c l e i n f o a b s t r a c t
Article history:
Received
14 September 2016
Received
in revised form 23 January 2017
Accepted
24 January 2017
Available
online 20 February 2017
Editor:
J. Hisano
A charged Higgs in the type II two-Higgs-doublet model (THDM) has been bounded to be above a few
hundred GeV by the radiative B decays. A Higgs triplet extension of the THDM not only provides an origin
of neutrino masses and a completely new doubly-charged Higgs decay pattern, but it also achieves a
light-charged Higgs with a mass of O(100) GeV through the new scalar couplings in the scalar potential.
It was found that these light-charged Higgs decays depend on its mass m
H
±
, tan β, and mixing effect
sin θ
±
: at tan β = 1, if m
H
±
> m
W
+ m
Z
,
¯
bbW
±
, W
±
Z, and τν are the main decay modes; however,
if m
H
±
< m
W
+ m
Z
, the main decay modes are then
¯
bbW and τν, and at tan β = 30, the τν mode
dominates the other decays. When m
t
> m
H
±
+ m
b
, we found that the ATLAS and CMS recent upper
bounds on the product of BR(t → H
+
b)BR(H
+
→ τ
+
ν) can be directly applied and will give a strict
constraint on the correlation of m
H
±
and sin θ
±
. If the upper bound of BR(t → H
+
b)BR(H
+
→ τ
+
ν)
is satisfied (escaped) for m
t
>(<)m
H
±
+ m
b
, it was found that the significance of discovering the
charged Higgs through H
±
→ W
±
Z is much lower than that through H
±
→
¯
bbW
±
. With a luminosity
of 100 fb
−1
at
√
s = 13 TeV and including the experimental bounds, the significance of the H
±
→
¯
bbW
±
signal can reach around 6.2(2.4)σ for m
H
±
<(>)m
W
+m
Z
.
© 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP
3
.
The two-Higgs-doublet model (THDM) is one of the minimal
extensions of the standard model (SM) in supersymmetric (SUSY)
and non-SUSY frameworks. The scalar bosons in the model com-
prise
two CP-even scalars (h, η
0
), one CP-odd pseudoscalar (χ
0
),
and two charged Higgs particles (η
±
). To avoid the flavor-changing
neutral currents at the tree level, a discrete symmetry is usually
imposed. Thus, several types of non-SUSY THDMs have been clas-
sified
in the literature according to the couplings to the fermions
in the Yukawa sector [1,2]; As such, different types of THDMs may
have different constraints on their masses and couplings.
With
the discovery of a new scalar via ATLAS [3] and CMS [4],
the mass of the SM-like Higgs h was determined to be m
h
≈
125 GeV. Without fine-tuning the parameters in the scalar poten-
tial,
the 2 × 2 mass-square matrix (M
2
) elements of the CP-even
scalars are expected to have the same order of magnitude. Due
to the sizable off-diagonal entries of M
2
, the mass-splitting be-
tween
the two CP-even Higgs bosons can reach a few hundred
GeV. For instance, if the diagonal and off-diagonal elements of M
2
*
Corresponding author.
E-mail
addresses: physchen@mail.ncku.edu.tw (C.-H. Chen), nomura@kias.re.kr
(T. Nomura).
are 500
2
GeV
2
and 300
2
GeV
2
, respectively, then the masses of the
CP-even bosons would be 126 GeV and 583 GeV.
Among
the classifications of the model, only the type II THDM
has the same Yukawa couplings as the minimal supersymmetric
standard model (MSSM). It is of importance that the charged Higgs
mass of this model is bounded to be m
η
±
> 480 GeV at the 95%
confidence
level (CL) [5] by the precision measurement of B →
X
s
γ [6]. Additionally, the constraint is insensitive to the parameter
tan β = v
2
/v
1
, where v
1(2)
is the vacuum expectation value (VEV)
of the Higgs doublet that couples to the up(down)-type quarks. As
a result, the charged Higgs in the type II THDM can not be a light
particle unless the model is further extended.
One
of the unsolved puzzles in particle physics is the origin
of neutrino masses. If we assume that the neutrino mass arises
from spontaneous symmetry breaking (SSB), like that in the SM
and THDM, the minimal extension of the THDM adds an SU(2)
Higgs triplet [7,8]. In addition to the new scalar bosons, such
as doubly-charged Higgses δ
±±
and neutral scalars (δ
0
, ξ
0
), apair
of new charged scalar bosons δ
±
exists in such models. Due to
the strict constraint from the precision measurement of the elec-
troweak
ρ-parameter [6], the VEV of (v
) is limited to v
<
3.4GeV. That is, before electroweak symmetry breaking (EWSB),
http://dx.doi.org/10.1016/j.physletb.2017.01.080
0370-2693/
© 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by
SCOAP
3
.