Physics Letters B 783 (2018) 140–149
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Loop effects on the Higgs decay widths in extended Higgs models
Shinya Kanemura
a
, Mariko Kikuchi
b,1
, Kentarou Mawatari
a,∗
, Kodai Sakurai
c,a
,
Kei Yagyu
d,2
a
Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan
b
Department of Physics, National Taiwan University, Taipei 10617, Taiwan
c
Department of Physics, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan
d
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
6 March 2018
Received
in revised form 23 May 2018
Accepted
14 June 2018
Available
online 19 June 2018
Editor: J.
Hisano
In order to identify the Higgs sector using future precision data, we calculate the partial decay widths
of the discovered Higgs boson with the mass of 125 GeV into fermion pairs and gauge-boson pairs with
one-loop electroweak and one-loop QCD corrections in various extended Higgs models, such as the Higgs
singlet model and four types of two Higgs doublet models. In the tree-level analysis, the patterns of
deviations from the standard model predictions in the partial decay widths for various decay modes
are distinctive for each model, due to the mixing of the Higgs boson with other neutral scalars. Our
present analysis shows that even with a full set of radiative corrections we can discriminate these
extended Higgs models via the partial decay widths as long as any of the deviations is detected at
future precision measurements. Furthermore, we quantitatively show that in each model the magnitude
of the deviations can provide important information on the mass scale of extra Higgs bosons under the
theoretical constraints from perturbative unitary and vacuum stability, which can be obtained without
discovery of the additional Higgs bosons.
© 2018 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
Except a resonance with the 125 GeV mass, the LHC experi-
ments
have not observed any other states expected by new physics
(NP) beyond the standard model (SM), and instead put limits on
them to higher and higher mass scales by increasing the collision
energy and accumulating more data. On the other hand, all the
measurements for the discovered particle agree with the predic-
tions
of the SM Higgs boson within the experimental uncertainty
so far [1]. Such situation highly motivates us a thorough study
of the Higgs sector at the LHC Run-II as well as in future high-
precision
experimental programs such as the high-luminosity LHC
(HL-LHC) [2,3] and future lepton colliders such as the international
linear collider (ILC) [4–6], the lepton collision option of the future
circular collider (FCC-ee) [7], the circular electron positron collider
(CEPC) [8] and the compact linear collider (CLIC) [9].
*
Corresponding author.
E-mail
address: kentarou.mawatari@het.phys.sci.osaka-u.ac.jp (K. Mawatari).
1
Address after April 2018, National Institute of Technology, Kitakyushu College,
5-20-1 Shii, Kokuraminamiku, Kitakyushu, Fukuoka, 802-0985 Japan.
2
Address after April 2018, Seikei University, Musashino, Tokyo 180-8633, Japan.
Although the SM takes the minimal setup for the Higgs sector;
i.e., a scalar isospin doublet field, there is no compelling reason
to be minimal, and indeed many NP models predict additional
scalar multiplets. For instance, the B −L extended SM [10] contains
an additional singlet scalar field, while the minimal supersym-
metric
SM has another doublet scalar field. Furthermore, some of
the scenarios for radiative seesaw models predict extended Higgs
sectors [11–17], and many of the scenarios of electroweak baryoge-
nesis
also require non-minimal structures for the Higgs sector [18–
20].
Therefore, by studying the structure of the Higgs sector by ex-
periments,
we may be able to determine the models of NP.
There
are two important consequences in models with a non-
minimal
Higgs sector. One is the existence of additional scalar
states, and the other is deviations of the interactions for the
SM-like Higgs boson from the SM prediction due to the mix-
ing
with other neutral scalars as well as loop effects of ad-
ditional
scalars. The current LHC Higgs program clearly targets
them [21], and has been seeking for extra scalars in the direct
searches [22–25] and looking for deviations in the Higgs coupling
measurements [1,22,26], which already put constraints on the pa-
rameter
space of extended Higgs models. In this work, we focus
on the latter aspect; i.e., deviations from the SM via precise mea-
surements
at the LHC as well as in the future experiments, where
https://doi.org/10.1016/j.physletb.2018.06.035
0370-2693/
© 2018 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
.