Physics Letters B 804 (2020) 135358
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Search for a generic heavy Higgs at the LHC
Xin Chen
a,b
, Yue Xu
a
, Yongcheng Wu
c
, Yu-Ping Kuang
a,b
, Qing Wang
a,b
, Hang Chen
a
,
Shih-Chieh Hsu
d
, Zhen Hu
a
,
b
, Congqiao Li
d
a
Department of Physics, Tsinghua University, Beijing 100084, China
b
Center for High Energy Physics, Tsinghua University, Beijing 100084, China
c
Ottawa-Carleton Institute for Physics, Carleton University, Ottawa, Ontario K1S 5B6, Canada
d
Department of Physics, University of Washington, Seattle, WA 98195, USA
a r t i c l e i n f o a b s t r a c t
Article history:
Received 16 July 2019
Received in revised form 14 February 2020
Accepted 5 March 2020
Available online 9 March 2020
Editor: A. Ringwald
Keywords:
Generic heavy Higgs
LHC
A generic heavy Higgs has both dim-4 and effective dim-6 interactions with the Standard Model (SM)
particles. The former has been the focus of LHC searches in all major Higgs production modes, just as the
SM one, but with negative results so far. If the heavy Higgs is connected with Beyond Standard Model
(BSM) physics at a few TeV scale, its dim-6 operators will play a very important role -they significantly
enhance the Higgs momentum, and reduce the SM background in a special phase space corner to a level
such that a heavy Higgs emerges, which is not possible with dim-4 operators only. We focus on the
associated VH production, where the effect of dim-6 operators is the largest and the SM background is
the lowest. Main search regions for this type of signal are identified, and substructure variables of boosted
jets are employed to enhance the signal from backgrounds. The parameter space of these operators are
scanned over, and expected exclusion regions with 300 fb
−1
and 3ab
−1
LHC data are shown, if no BSM
is present. The strategy given in this paper will shed light on a heavy Higgs which may be otherwise
hiding in the present and future LHC data.
© 2020 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. Effective couplings of a heavy Higgs
It is not very natural that the SM has only one fundamental
scalar field -the Higgs field. If Nature really chooses this way, there
must be something else unknown to us as yet. An alternative, and
natural, way is that the 125 GeV Higgs boson discovered at the
LHC [1]-[2]may be the lightest Higgs scalar field, among many that
have yet to be found. Heavy Higgs particles are predicted in many
BSM theories, such as the two-Higgs-doublet models, the minimal
supersymmetric extension of the SM, and the left-right symmetric
models. In a multiple Higgs field theory, the original Higgs fields
are
1
,
2
, ······.
1
The multi-Higgs potential will cause mixing
among them to form the mass eigenstates. Let
h
and
H
be the
two doublets containing the lightest (h) and next to lightest (H)
neutral Higgs respectively. The couplings to the SM gauge bosons
E-mail addresses: xin.chen@cern.ch (X. Chen), yue.xu@cern.ch (Y. Xu),
ycwu@physics.carleton.ca (Y. Wu).
1
In general, they can be in any allowed SU(2)
L
representations. For simplicity,
we will just illustrate the case where all fields are doublet.
will be scaled due to the mixing compared with SM gauge cou-
pling.
At leading order, the dim-4 operators can be written as
L
(4)
hW W
=ρ
h
gm
W
hW
μ
W
μ
,
L
(4)
hZ Z
=ρ
h
gm
W
2cos
2
θ
W
hZ
μ
Z
μ
,
L
(4)
HWW
=ρ
H
gm
W
HW
μ
W
μ
,
L
(4)
HZZ
=ρ
H
gm
W
2cos
2
θ
W
HZ
μ
Z
μ
, (1)
where θ
W
is the weak mixing angle, m
W
the W boson mass, ρ
h
and ρ
H
are the scaling factors. In the simplest 2HDM example, we
will have ρ
h
=cos(β − α), ρ
H
=sin(β − α).
For a SM-like light Higgs, ρ
h
is not far away from 1. Generally,
for a heavy Higgs H, there could also be dim-6 effective operators
which is related to an even higher energy scale BSM physics [3]:
L
(6)
HVV
=
n
f
n
2
O
n
, (2)
https://doi.org/10.1016/j.physletb.2020.135358
0370-2693/© 2020 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
.