2011 QCD and High Energy Interactions - Rencontres de Moriond ...

SUSY searches in CMS
M. Chiorboli
on behalf of the CMS Collaboration
CERN, 1211 Geneva 23, Switzerland
Istituto Nazionale di Fisica Nucleare, Via Enrico Fermi 40 - 00044 Frascati (Rome), Italy
Dipartimento di Fisica e Astronomia dell’Università di Catania, Via S. Sofia 64 - 95123 Catania, Italy
In the 2010 data taking period, the CMS experiment collected 36 pb −1 of integrated luminosity.
An overview of the analyses performed on this dataset in the search for supersymmetric events
is presented. No significant excess with respect to the backgrounds expected from the Standard
Model has been observed in any final state. Exclusion regions beyond previous experiment
searches are set, and a robust strategy is defined to make discoveries in the 2011-2012 LHC
run
1 Analysis strategy
The strategy of the CMS Collaboration in the search for Supersymmetric events is based on one
fundamental assumption: we don’t know how Physics beyond the Standard Model will manifest
itself. The guideline is hence not to follow the models, and to design instead a set of inclusive
analyses based uniquely on the final states. This set of analyses has to be complete and robust.
For a given final state, different approaches can be chosen to increase the robustness of the
analysis.
2 Supersymmetry at CMS
The Supersymmetric analyses are performed using the physics objects reconstructed in the
CMS detector 1 : electrons, muons, taus, photons, jets, missing transverse energy (MET), HT
(the scalar sum of the jet transverse energies), MHT (the vectorial sum of the jet transverse
energies). They have all been commissioned and understood during the initial stages of the 2010
run.
The analyses are essentially counting experiments: an excess of events is searched out of
an estimated Standard Model background. Whenever possible, the backgrounds are estimated
with data-driven methods. To make the analyses even more robust, the same background is
often estimated with multiple data-driven methods. The cuts are not optimized to maximize
the exclusion regions: the aim of the analyses is not to just define stringent exclusion limits, but
to establish the methods needed to be ready for discoveries.
3 Fully Hadronic final states
Different approaches are used in the search for Supersymmetric events with jets and missing
transverse energy in the final state. The first approach is based on the variable αT 2 , used