Physics Letters B 756 (2016) 337–344
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Physics Letters B
www.elsevier.com/locate/physletb
Renormalizable model for neutrino mass, dark matter, muon g −2and
750 GeV diphoton excess
Hiroshi Okada
a,b,∗
, Kei Yagyu
c
a
School of Physics, KIAS, Seoul 130-722, Republic of Korea
b
Physics Division, National Center for Theoretical Sciences, Hsinchu, 300, Taiwan
c
School of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ, United Kingdom
a r t i c l e i n f o a b s t r a c t
Article history:
Received
26 February 2016
Accepted
15 March 2016
Available
online 18 March 2016
Editor:
J. Hisano
We discuss a possibility to explain the 750 GeV diphoton excess observed at the LHC in a three-loop
neutrino mass model which has a similar structure to the model by Krauss, Nasri and Trodden. Tiny
neutrino masses are naturally generated by the loop effect of new particles with their couplings and
masses to be of order 0.1–1 and TeV, respectively. The lightest right-handed neutrino, which runs in the
three-loop diagram, can be a dark matter candidate. In addition, the deviation in the measured value of
the muon anomalous magnetic moment from its prediction in the standard model can be compensated
by one-loop diagrams with exotic multi-charged leptons and scalar bosons. For the diphoton event, an
additional isospin singlet real scalar field plays the role to explain the excess by taking its mass of
750 GeV, where it is produced from the gluon fusion production via the mixing with the standard model
like Higgs boson. We find that the cross section of the diphoton process can be obtained to be a few fb
level by taking the masses of new charged particles to be about 375 GeV and related coupling constants
to be order 1.
© 2016 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
.
1. Introduction
In December 2015, the both ATLAS and CMS groups have re-
ported
the existence of the excess at around 750 GeV in the dipho-
ton
distribution at the Large Hadron Collider (LHC) with the colli-
sion
energy of 13 TeV. The local significance of this excess is about
3.6σ at ATLAS [1] with the integrated luminosity of 3.2fb
−1
and
about 2.6σ at CMS [2] with the integrated luminosity of 2.6fb
−1
.
The detailed properties of the diphoton excess were summarized,
e.g., in Ref. [3], where the best fit value of the width of the new
resonance is about 45 GeV, and the estimated cross section of the
diphoton signature is 10 ± 3fbat ATLAS and 6 ± 3fbat CMS. If
this excess is confirmed by future data, it suggests the existence
of a new particle which gives the direct evidence of a new physics
beyond the standard model (SM).
The
simplest way to explain this excess is to consider an ex-
tension
of the SM by adding extra isospin scalar multiplets such
as a singlet, a doublet and/or a triplet. However, it is difficult to
*
Corresponding author.
E-mail
address: hokada@kias.re.kr (H. Okada).
get a sufficient cross section to explain the excess as mentioned
in the above in such a simple extension of the SM. For exam-
ple,
if we consider the CP-conserving two Higgs doublet models
(THDMs) [4–7], and take the masses of the additional CP-even H
and
CP-odd A Higgs bosons to be 750 GeV, then the cross sec-
tion
of pp → H/A → γγ is typically three order smaller than the
required value [4]. Therefore, we need to further introduce ad-
ditional
sources to get an enhancement of the production cross
section and/or the branching fraction to the diphoton mode, e.g.,
by introducing multi-charged scalar particles [4,6] and vector-like
fermions [7]. In Refs. [8], the diphoton excess has been discussed
in supersymmetric models.
In
this paper, we discuss a scenario to naturally introduce multi-
charged
particles to get an enhancement of the branching frac-
tion.
Namely, we consider a radiative neutrino mass model in
which multi-charged particles play a role not only to increase
the branching fraction but also to explain the smallness of neu-
trino
masses and the anomaly of the muon anomalous magnetic
moment. Adark matter (DM) candidate can also successfully be
involved as a part of the model. There are a few papers discussing
the diphoton excess within radiative neutrino mass models [9].
http://dx.doi.org/10.1016/j.physletb.2016.03.040
0370-2693/
© 2016 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
.