Abstract
Abstract A search for supersymmetry or other new physics resulting in similar final states is presented using a data sample of 4.73 fb−1 of pp collisions collected at $ \sqrt{s}=7 $ TeV with the CMS detector at the LHC. Fully hadronic final states are selected based on the variable M T2, an extension of the transverse mass in events with two invisible particles. Two complementary studies are performed. The first targets the region of parameter space with medium to high squark and gluino masses, in which the signal can be separated from the standard model backgrounds by a tight requirement on M T2. The second is optimized to be sensitive to events with a light gluino and heavy squarks. In this case, the M T2 requirement is relaxed, but a higher jet multiplicity and at least one b-tagged jet are required. No significant excess of events over the standard model expectations is observed. Exclusion limits are derived for the parameter space of the constrained minimal supersymmetric extension of the standard model, as well as on a variety of simplified model spectra.
Highlights
Background prediction6.1.1 QCD multijet backgroundThe simulation predicts that the QCD multijet background is negligible in the tail of the MT2 distribution
The selection criteria developed for the MT2 analysis are not optimal for events with heavy squarks and light gluinos, such as are predicted by the SUSY benchmark model LM9
We have conducted a search for supersymmetry or similar new physics in hadronic final states using the MT2 variable calculated from massless pseudojets
Summary
The variable MT2 was introduced [2] to measure the mass of primary pair-produced particles in a situation where both decay into undetected particles (e.g., LSPs) leaving the event kinematics underconstrained It assumes that the two produced sparticles give rise to identical types of decay chains with two visible systems defined by their transverse momenta pTvis(i), transverse energies ETvis(i), and masses mvis(i). QCD multijet events with large ETmiss may give rise to acoplanar pseudojets, leading to larger MT2 values. For this reason, further protections against ETmiss from mismeasurements need to be introduced, as described below. Other SM backgrounds, such as tt, single top-quark, and W+jets events with leptonic decays, or Z+jets events where the Z boson decays to neutrinos, contain true ETmiss and can lead to acoplanar pseudojets
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