Physics Letters B 774 (2017) 119–122
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Radiative corrections to Higgs couplings with weak gauge bosons
in custodial multi-Higgs models
Cheng-Wei Chiang
a,b,c,d
, An-Li Kuo
e
, Kei Yagyu
f,∗
a
Department of Physics, National Taiwan University, Taipei, 10617, Taiwan, ROC
b
Institute of Physics, Academia Sinica, Taipei, 11529, Taiwan, ROC
c
Physics Division, National Center for Theoretical Sciences, Hsinchu, 30013, Taiwan, ROC
d
Kavli IPMU, University of Tokyo, Kashiwa, 277-8583, Japan
e
Department of Physics, National Central University, Chungli, 32001, Taiwan, ROC
f
INFN, Sezione di Firenze, and Department of Physics and Astronomy, University of Florence, Via G. Sansone 1, 50019 Sesto Fiorentino, Italy
a r t i c l e i n f o a b s t r a c t
Article history:
Received
25 August 2017
Received
in revised form 20 September
2017
Accepted
21 September 2017
Available
online 22 September 2017
Editor:
J. Hisano
We calculate 1-loop radiative corrections to the hZ Z and hW W couplings in models with next-to-
simplest
Higgs sectors satisfying the electroweak ρ parameter equal to 1 at tree level: the real Higgs
singlet model, the two-Higgs doublet models, and the Georgi–Machacek model. Under theoretical and
current experimental constraints, the three models have different correlations between the deviations in
the hZ Z and hW W couplings from the standard model predictions. In particular, we find for each model
predictions with no overlap with the other two models.
© 2017 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 particle spectrum of the Standard Model (SM) has been
completed by the discovery of a Higgs boson (h) at the LHC, of
which properties are found to be consistent with SM expectations
within uncertainties. However, it is widely accepted that the SM
should be replaced by a more fundamental theory at a higher en-
ergy
scale to address such issues as the origin of neutrino masses
and the existence of dark matter among others. A pressing task in
particle physics is to search for new particles in or footprints left
by such new physics (NP) in current and future experiments.
Since
many NP models predict a non-minimal structure in their
Higgs sector, determining its true shape turns out to be an im-
portant
probe of physics beyond the SM. If we discover a second
Higgs boson in future collider experiments, this must be direct
evidence of a non-minimal Higgs sector. In that case, by measur-
ing
its properties, such as mass, width and cross sections, we can
reconstruct the structure of the Higgs sector. Alternatively, a non-
minimal
Higgs sector can be explored indirectly by measuring the
h couplings to other SM particles including itself. If non-zero de-
viations
in h couplings from the SM predictions are found with
a specific pattern, we can extract information of the Higgs sector
such as the representation of extra scalar fields by comparing mea-
*
Corresponding author.
E-mail
address: yagyu@fi.infn.it (K. Yagyu).
sured values with theory predictions [1]. Therefore, albeit indirect,
a precision determination of the h couplings is an effective probe
of NP, particularly when new Higgs bosons are beyond the reach
of available colliders.
As
experimental precision becomes higher, we are forced to go
beyond the tree-level calculation for the h couplings in order to
make a sensible comparison. In particular, the hZZ and hW W
couplings
will be measured with higher precisions (better than 1%
level) than the others at future e
+
e
−
colliders, e.g., the Interna-
tional
Linear Collider (ILC) [2]. Therefore, precise calculations of
these couplings by taking into account electroweak radiative cor-
rections
are inevitable for future comparisons.
In
this Letter, we study deviations in the hZ Z and hW W cou-
plings
from their SM predictions at 1-loop level in models having
a non-minimal Higgs sector with electroweak ρ parameter equal
to 1 at tree level (ρ
tree
= 1). In such models, the coupling rela-
tion
g
hW W
= g
hZZ
cos
2
θ
W
with θ
W
being the weak mixing angle
is satisfied at tree level. However, this is no longer valid in general
when loop effects are taken into account, as they receive different
radiative corrections. We will show different characteristic devia-
tions
in these couplings at 1-loop level for different models.
2. Renormalized hV V vertex
First of all, we define the renormalized hV
μ
V
ν
vertices (V =
Z, W ) in the SU(2)
L
× U (1)
Y
gauge theory, in which the Higgs
sector is assumed to have at least one SU(2)
L
doublet field. In
https://doi.org/10.1016/j.physletb.2017.09.061
0370-2693/
© 2017 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
.