Physics Letters B 772 (2017) 426–434
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Search for heavy neutral CP-even Higgs within lepton-specific 2HDM
at a future linear collider
Majid Hashemi
∗
, Gholamhossein Haghighat
Physics Department, College of Sciences, Shiraz University, Shiraz, 71946-84795, Iran
a r t i c l e i n f o a b s t r a c t
Article history:
Received
22 April 2017
Received
in revised form 18 June 2017
Accepted
29 June 2017
Available
online 17 July 2017
Editor:
A. Ringwald
Keywords:
2HDM
Higgs
Boson
Linear
Collider
In this paper, the production process e
−
e
+
→ AH is analyzed in the context of the lepton-specific (or
type IV) 2HDM and the question of observability of a neutral CP-even Higgs boson H at a linear collider
operating at
√
s = 1TeV is addressed. The CP-odd Higgs is assumed to experience a gauge-Higgs decay
as A → ZH with hadronic decay of Z boson as the signature of signal events. The production chain
is thus e
+
e
−
→ AH → ZHH → jj where is a τ or μ. Four benchmark points with different
mass hypotheses are assumed for the analysis. The Higgs mass m
H
is assumed to vary within the range
150–300 GeV in increments of 50 GeV. The anti-k
t
algorithm is used to perform the jet reconstruction.
Results indicate that the neutral CP-even Higgs H is observable through this production mechanism using
the di-muon invariant mass distribution with possibility of mass measurement. The corresponding signal
significances exceed 5σ at integrated luminosity of 3000 fb
−1
.
© 2017 The Author(s). 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
.
1. Introduction
The standard model of elementary particles has been confirmed
by a large number of experimental tests and its success has at-
tracted
attention on possible extensions of the theory which may
pave the way for a solution to the present serious and challenging
problems in physics. The discovery of the first elementary scalar
particle, the Higgs boson [1,2], which was a prediction of the Higgs
mechanism [3–8], has strengthened the idea that multiple Higgs
bosons may exist in nature and the discovered SM Higgs may be
only one of them. In the SM, the simplest possible scalar structure
is assumed. However, supersymmetry [9], axion models [10], the
SM inability to explain the baryon asymmetry of the universe [11],
etc., have been some important motivations behind the idea of ex-
tending
the SM by adding another SU(2) Higgs doublet. Assuming
two SU(2) Higgs doublets instead of a single doublet forms one
of the simplest extensions of the SM, i.e., the two-Higgs-doublet
model (2HDM) [12–18].
In
comparison with the SM, probing the entire parameter space
of 2HDMs takes much longer because of the large number of free
parameters in these models. 2HDMs predict more than one Higgs
particle. In order to respect the experimental observations, one of
the Higgs bosons (the lightest one) is assumed to be the same
*
Corresponding author.
E-mail
addresses: hashemi_mj@shirazu.ac.ir (M. Hashemi),
hosseinhaqiqat@gmail.com (G. Haghighat).
as the SM Higgs boson. Other than the SM-like Higgs boson h,
two other neutral Higgs bosons A and H, and two charged Higgs
bosons H
±
are predicted in 2HDMs. In this work the observability
of the scalar CP-even neutral Higgs H is studied.
The
production process e
+
e
−
→ AH → ZHH followed by the
decays Z → jj and HH → ττμμ or μμτ τ is assumed in this
work to take advantage of the clear signal that leptonic decays
can provide at linear colliders. From the four types of the 2HDM
which conserve flavour, the lepton-specific type (hereafter briefly
referred to as type IV) is chosen as the theoretical framework to
enhance the Higgs leptonic decay at high tan β by utilizing the key
role tan β plays [19]. This enhancement is caused by the appear-
ance
of cot β and tan β factors in Higgs-quark and Higgs-lepton
couplings respectively in the Yukawa lagrangian. τ -jets in the final
decay products are identified by performing a τ -tagger algorithm
and it is expected that the di-muon invariant mass distribution
will provide an observable signal on top of the background.
Contrary
to the Minimal Supersymmetric Standard Model
(MSSM) [9,20–22] which constrains the Higgs masses, Higgs
masses of the 2HDM are allowed to have arbitrary values in gen-
eral.
Therefore, 2HDMs provide a wider mass parameter space.
In this work, four benchmark points in the Higgs mass param-
eter
space are defined and a simulation is performed for each
one to assess the observability of the neutral Higgs H . It will be
shown that the signal is observable and the H mass reconstruc-
tion
is possible for all of the four assumed benchmark points.
In [23] a similar signal in the context of type IV 2HDM with
http://dx.doi.org/10.1016/j.physletb.2017.06.068
0370-2693/
© 2017 The Author(s). 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
.