Abstract
Results are presented from a search for natural gauge-mediated supersymmetry (SUSY) in a scenario in which the top squark is the lightest squark, the next-to-lightest SUSY particle is a bino-like neutralino, and the lightest SUSY particle is the gravitino. The strong production of top squark pairs can produce events with pairs of top quarks and neutralinos, with each bino-like neutralino decaying to a photon and a gravitino. The search is performed using a sample of pp collision data accumulated by the CMS experiment at sqrt{s}=8 TeV, corresponding to an integrated luminosity of 19.7 fb−1. The final state consists of a lepton (electron or muon), jets, and one or two photons. The imbalance in transverse momentum in the events is compared with the expected spectrum from standard model processes. No excess event yield is observed beyond the expected background, and the result is interpreted in the context of a general model of gauge-mediated SUSY breaking that leads to exclusion of top squark masses below 650–730 GeV.
Highlights
The strong production of top squark pairs can produce events with pairs of top quarks and neutralinos, with each bino-like neutralino decaying to a photon and a gravitino
No excess event yield is observed beyond the expected background, and the result is interpreted in the context of a general model of gauge-mediated SUSY breaking that leads to exclusion of top squark masses below 650–730 GeV
All backgrounds are simulated using Monte Carlo (MC) generated events and assigned systematic uncertainties based on integrated luminosity uncertainties, Parton distribution functions (PDF) and scale uncertainties, corrections for the number of pileup events, and jet energy scale and resolution (JES and JER)
Summary
The central feature of the CMS detector is a superconducting solenoid with an internal diameter of 6 m, providing a magnetic field of 3.8 T. A silicon pixel and strip tracker, a lead tungstate crystal electromagnetic calorimeter (ECAL), and a brass and scintillator sampling hadron calorimeter (HCAL), each separated into central barrel and endcap sections, reside within the field volume. Extensive forward calorimetry complements the coverage provided by the barrel and endcap detectors. Photons located in the barrel of the ECAL are considered in this analysis because of the superior energy resolution in the barrel compared to the endcap. The first level of the CMS trigger system, constructed using special hardware processors, provides information from the calorimeters and muon detectors to select the most interesting events in a fixed time interval of less than 4 μs. A more detailed description of the CMS detector, together with a definition of the coordinate system and the kinematic variables, such as η or the azimuthal angle φ (in radians), can be found in ref. [39]
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