Physics Letters B 735 (2014) 412–416
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Connecting simplified models: Constraining supersymmetry
on triangles
Archana Anandakrishnan
∗
, Christopher S. Hill
Department of Physics, The Ohio State University, 191 W. Woodruff Ave, Columbus, OH 43210, USA
a r t i c l e i n f o a b s t r a c t
Article history:
Received
19 March 2014
Received
in revised form 20 June 2014
Accepted
23 June 2014
Available
online 26 June 2014
Editor:
L. Rolandi
Keywords:
Supersymmetry
SUSY
Simplified
models
Triangles
We investigate an approach for the presentation of experimental constraints on supersymmetric
scenarios. It is a triangle-based visualization that extends the status quo wherein the LHC results are
reported in terms of simplified models under the assumption of 100% branching ratios. We show that
the (re)interpretation of the LHC data on triangles allows the extraction of accurate exclusion limits for
a multitude of more realistic models with arbitrary branching ratios. We demonstrate the utility of this
triangle visualization approach using the example of gluino production and decay in several common
supersymmetric scenarios.
© 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/3.0/). Funded by SCOAP
3
.
1. Introduction
The extent to which supersymmetric scenarios are excluded by
data from the LHC experiments is obscured by the breadth of re-
alizations
with which such scenarios might manifest themselves.
In order to make this problem more tractable while avoiding the
prejudices of specific UV completions (e.g. CMSSM), the ATLAS and
CMS experiments have adopted the strategy of distilling theoretical
scenarios into “Simplified Models” [1–3] that reduce the parame-
ters
of the theory to those that directly affect the experimental
observability of the supersymmetric signal. While this has been
a significant improvement in the way the LHC experimental con-
straints
on supersymmetry are presented, this approach also has a
number of shortcomings. In this Letter, we present an extension of
the simplified model approach that addresses one such limitation,
namely the commonly made, though often unrealistic assumption
that any new particles produced will have 100% Branching Ratio
(BR) into the experimental final states over which the search is
conducted.
In
this work we will focus on the gluino as an example of a
SUSY particle where the existence of a number of possible decay
modes complicates the interpretation of the experimental results
produced by the LHC collaborations. Even in scenarios in which
the gluino decays only to the lightest neutralino plus a quark–
*
Corresponding author.
E-mail
addresses: archana@physics.osu.edu (A. Anandakrishnan),
chill@physics.osu.edu (C.S. Hill).
antiquark pair, there are distinct possibilities for the decay that
are optimized with different search strategies. In principle, the
possibility of two different decay modes for a pair-produced super-
symmetric
particle could significantly weaken the exclusion limits
obtained by assuming 100% BR into the final states considered in
the experimental search. The triangle approach we adopt here for
presentation of the experimental limits allows one to visualize this
effect.
2. Points on the triangle
By definition, the sum of a particle’s branching ratios add up to
one. A particle with 100% BR into a single set of final states repre-
sents
a Simplified Model Scenario (SMS) which is a single point on
the parameter space of all possible models of the particle. Mod-
els
with branching ratios of a particle into two independent final
states all lie on a straight line given the constraint on the total
branching ratio. Similarly, all models of the particle with three in-
dependent
decay modes are confined to a triangle since there are
only two free parameters. Note that models with greater than 3
decay final states cannot be visualized in the same manner on a
2-dimensional plot. Nevertheless, all models with up to three de-
cay
final states can be presented by adopting the triangle visualiza-
tion
method. Let us denote the three decay branching fractions of
a supersymmetric particle as B
A
, B
B
, and B
C
. The space spanned
by scanning over values of (B
A
, B
B
, B
C
) is a triangular plane. Each
point on the 2-dimensional space can be written in terms of the
branching ratios as:
http://dx.doi.org/10.1016/j.physletb.2014.06.059
0370-2693/
© 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/). Funded by
SCOAP
3
.