Abstract
A search for the production of a pair of top squarks at the LHC is presented. This search targets a region of parameter space where the kinematics of top squark pair production and top quark pair production are very similar, because of the mass difference between the top squark and the neutralino being close to the top quark mass. The search is performed with 35.9 fb−1 of proton-proton collisions at a centre-of-mass energy of sqrt{s}=13 TeV, collected by the CMS detector in 2016, using events containing one electron-muon pair with opposite charge. The search is based on a precise estimate of the top quark pair background, and the use of the MT2 variable, which combines the transverse mass of each lepton and the missing transverse momentum. No excess of events is found over the standard model predictions. Exclusion limits are placed at 95% confidence level on the production of top squarks up to masses of 208 GeV for models with a mass difference between the top squark and the lightest neutralino close to that of the top quark.
Highlights
A search for the production of a pair of top squarks at the LHC is presented. This search targets a region of parameter space where the kinematics of top squark pair production and top quark pair production are very similar, because of the mass difference between the is performed top squark and the neutralino being close with 35.9 fb−1 of proton-proton collisions to at the top quark mass
This paper presents a search for the production of a pair of scalar top partners and neutralinos that are degenerate or nearly degenerate in mass with the top quark, using events produced in pp collisions at a centre-of-mass energy of 13 TeV recorded with the CMS detector at the LHC
To account for particles produced in pileup interactions, the contribution from charged hadrons that are not associated to the primary vertex is removed and a correction is applied for the expected contribution of neutral hadrons, following the procedure in [64]
Summary
The central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter, providing a magnetic field of 3.8 T. Forward calorimeters extend the pseudorapidity coverage provided by the barrel and endcap detectors. Events of interest are selected using a two-tiered trigger system [34]. The first level, composed of custom hardware processors, uses information from the calorimeters and muon detectors to select events at a rate of around 100 kHz within a time interval of less than 4 μs. The second level, known as the high-level trigger, consists of a farm of processors running a version of the full event reconstruction software optimized for fast processing, and reduces the event rate to around 1 kHz before data storage. A more detailed description of the CMS detector, together with a definition of the coordinate system used and the relevant kinematic variables, can be found in ref. [35]
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