https://doi.org/10.1140/epjc/s10052-011-1737-8
Special Article - Tools for Experiment and Theory
Improved sensitivity to charged Higgs searches in top quark decays t→bH +→b(τ + ν τ ) at the LHC using τ polarisation and multivariate techniques
1
Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
2
Facultad de Ciencias C-XI, Departamento de Fisica, Universidad Autonoma de Madrid (UAM), Cantoblanco, Madrid, 28049, Spain
* e-mail: ahmed.ali@desy.de
Received:
14
March
2011
Revised:
7
July
2011
Published online:
8
September
2011
We present an analysis with improved sensitivity to the light charged Higgs () searches in the top quark decays t→bH
+→b(τ
+
ν
τ
)+c.c. in the
and single
production processes at the LHC. In the Minimal Supersymmetric Standard Model (MSSM), one anticipates the branching ratio
over almost the entire allowed
range. Noting that the τ
+ arising from the decay H
+→τ
+
ν
τ
are predominantly right-polarized, as opposed to the τ
+ from the dominant background W
+→τ
+
ν
τ
, which are left-polarized, a number of H
+/W
+→τ
+
ν
τ
discriminators have been proposed and studied in the literature. We consider hadronic decays of the τ
±, concentrating on the dominant one-prong decay channel τ
±→ρ
±
ν
τ
. The energy and p
T
of the charged prongs normalised to the corresponding quantities of the ρ
± are convenient variables which serve as τ
± polariser. We use the distributions in these variables and several other kinematic quantities to train a boosted decision tree (BDT). Using the BDT classifier, and a variant of it called BDTD, which makes use of decorrelated variables, we have calculated the BDT(D)-response functions to estimate the signal efficiency vs. the rejection of the background. We argue that this chain of analysis has a high sensitivity to light charged Higgs searches up to a mass of 150 GeV in the decays t→bH
+ (and charge conjugate) at the LHC. For the case of single top production, we also study the transverse mass of the system determined using Lagrange multipliers.
© Springer-Verlag / Società Italiana di Fisica, 2011