Physics Letters B 760 (2016) 697–705
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Optimising charged Higgs boson searches at the Large Hadron Collider
across b
¯
bW
±
final states
Stefano Moretti
a
, Rui Santos
b,c
, Pankaj Sharma
d,∗
a
School of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ, United Kingdom
b
Centro de Física Teórica e Computacional, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, Edifício C8, 1749-016 Lisboa, Portugal
c
ISEL – Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa, 1959-007 Lisboa, Portugal
d
CoEPP – Center of Excellence in Particle Physics at Tera Scale, The University of Adelaide, 5005 Adelaide, South Australia, Australia
a r t i c l e i n f o a b s t r a c t
Article history:
Received
27 April 2016
Received
in revised form 13 June 2016
Accepted
21 July 2016
Available
online 26 July 2016
Editor:
G.F. Giudice
In the light of the most recent data from Higgs boson searches and analyses, we re-assess the scope of
the Large Hadron Collider in accessing heavy charged Higgs boson signals in b
¯
bW
±
final states, wherein
the contributing channels can be H
+
→ t
¯
b, hW
±
, HW
±
and AW
±
. We consider a 2-Higgs Doublet
Model Type-II and we assume as production mode bg → tH
−
+ c.c., the dominant one over the range
M
H
±
≥ 480 GeV, as dictated by b → sγ constraints. Prospects of detection are found to be significant for
various Run 2 energy and luminosity options.
© 2016 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 discovery of a (singly) charged Higgs boson would signal
the existence of a second Higgs doublet in addition to the Standard
Model (SM)-like one already established through the discovery of
the W
±
and Z bosons at the Sp
¯
pSin the eighties and of a Higgs
boson itself at the LHC only four years ago. Such a scalar field can
naturally be accommodated in 2-Higgs Doublet Models (2HDMs).
In its CP-conserving versions, they present in their spectra, after
spontaneous Electro-Weak Symmetry Breaking (EWSB), five physi-
cal
Higgs states: the neutral pseudoscalar (A), the lightest (h) and
heaviest (H ) neutral scalars and two charged ones (H
±
).
Of
all 2HDM Yukawa types (see Ref. [1] for a review), we con-
centrate
here on the 2HDM Type II (2HDM-II). Herein, constraints
from b → sγ decays put a lower limit on the H
±
mass at about
480 GeV, rather independently of tan β [2], the ratio of the Vac-
uum
Expectation Values (VEVs) of the two doublets. Such a heavy
mass region is very difficult to access because of the large re-
ducible
and irreducible backgrounds associated with the main de-
cay
mode H
+
→ t
¯
b, following the dominant production channel
bg → tH
−
[3]. (Notice that the rate of the latter exceeds by far
other possible production modes [4–6], thus rendering it the only
viable channel at the CERN machine in the heavy mass region.) The
analysis of the H
+
→ t
¯
b signature has been the subject of many
*
Corresponding author.
E-mail
addresses: s.moretti@soton.ac.uk (S. Moretti), rasantos@fc.ul.pt
(R. Santos),
pankaj.sharma@adelaide.edu.au (P. Sharma).
early debates [7–11], their conclusion being that the LHC discovery
potential might be satisfactory, so long that tan β is small (≤ 1.5)
or large (≥30) enough and the charged Higgs boson mass is below
600 GeV or so. Such positive prospects have very recently been re-
vived
by an ATLAS analysis of the full Run 1 sample [12], which
searched precisely for the aforementioned H
±
production and de-
cay
modes, by exploring the mass range 200 to 600 GeV using
multi-jet final states with one electron or muon. This study used
multivariate analysis techniques in the signal-rich region while it
employed control regions to reduce the large uncertainties on the
backgrounds. An excess of data with respect to the SM predictions
was observed for all H
±
mass hypotheses up to (but excluding)
600 GeV. While CMS does not confirm such an excess [13], the in-
creased
sensitivity that the two experiments are accruing with the
first Run 2 data calls for a renewed interest in this respect.
In
this spirit, and recognising that the H
+
→ t
¯
b decay chan-
nel
eventually produces a b
¯
bW
+
signature, Ref. [14] attempted
to extend the reach afforded by this channel by exploiting the
companion signature H
+
→ h
SM
W
+
→ b
¯
bW
+
, where h
SM
is the
SM-like Higgs boson discovered at CERN in 2012 (either h or H
in
2HDMs). The knowledge of its mass now provides in fact an
additional handle in the kinematic selection when reconstruct-
ing
a Breit–Wigner resonance in the h
SM
→ b
¯
b decay channel,
thereby significantly improving the signal-to-background ratio af-
forded
by pre-Higgs-discovery analyses [15,16]. Such a study found
that, while this channel does not show much promise for a super-
symmetric
H
±
state, significant portions of the parameter spaces
of several 2HDMs are testable at Run 2.
http://dx.doi.org/10.1016/j.physletb.2016.07.055
0370-2693/
© 2016 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
.