Abstract
A search for pair production of supersymmetric particles in events with two oppositely charged leptons (electrons or muons) and missing transverse momentum is reported. The data sample corresponds to an integrated luminosity of 35.9 fb−1 of proton-proton collisions at sqrt{s}=13 TeV collected with the CMS detector during the 2016 data taking period at the LHC. No significant deviation is observed from the predicted standard model background. The results are interpreted in terms of several simplified models for chargino and top squark pair production, assuming R-parity conservation and with the neutralino as the lightest supersymmetric particle. When the chargino is assumed to undergo a cascade decay through sleptons, with a slepton mass equal to the average of the chargino and neutralino masses, exclusion limits at 95% confidence level are set on the masses of the chargino and neutralino up to 800 and 320 GeV, respectively. For top squark pair production, the search focuses on models with a small mass difference between the top squark and the lightest neutralino. When the top squark decays into an off-shell top quark and a neutralino, the limits extend up to 420 and 360 GeV for the top squark and neutralino masses, respectively.
Highlights
Background estimationThe main contributions from SM processes to the signal region (SR) comes from tt, tW, and WW production
As top squark pair production occurs via strong interactions, a different set of reweighting factors is derived as a function of the multiplicity of initial-state radiation (ISR) jets (NjIeStR) in a sample of tt events selected by requiring an OC electron-muon pair and two jets identified as coming from bottom quark hadronization
Uncertainties due to signal and background normalizations are included through nuisance parameters with log-normal prior distributions, while uncertainties in the shape of the mT2( ) distributions are included with Gaussian prior distributions
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. In the inner part of the solenoid volume is a silicon pixel and strip tracker, which reconstructs the trajectories of the charged particles up to a pseudorapidity |η| < 2.5. A lead tungstate crystal electromagnetic calorimeter (ECAL) and a brass and scintillator hadron calorimeter (HCAL), each composed of a barrel and two endcap sections, measure the energy of the particles in the region |η| < 3. Forward calorimeters extend coverage provided by the barrel and endcap detectors up to |η| < 5. The information from the tracker and calorimeter systems is merged to reconstruct electrons and hadronic jets. 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. [19]
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