Abstract
A search is presented for single top quark production in the s channel in proton-proton collisions with the CMS detector at the CERN LHC in decay modes of the top quark containing a muon or an electron in the final state. The signal is extracted through a maximum-likelihood fit to the distribution of a multivariate discriminant defined using boosted decision trees to separate the expected signal contribution from background processes. The analysis uses data collected at centre-of-mass energies of 7 and 8 TeV and corresponding to integrated luminosities of 5.1 and 19.7 inverse femtobarns, respectively. The measured cross sections of 7.1 +/- 8.1 pb (at 7 TeV) and 13.4 +/- 7.3 pb (at 8 TeV) result in a best fit value of 2.0 +/- 0.9 for the combined ratio of the measured and expected values. The signal significance is 2.5 standard deviations, and the upper limit on the rate relative to the standard model expectation is 4.7 at 95% confidence level.
Highlights
A search is presented for single top quark production in the s channel in proton-proton collisions with the CMS detector at the CERN LHC in decay modes of the top quark containing a muon or an electron in the final state
The s channel production process is of special interest since a possible deviation from the SM prediction of its cross section may indicate the presence of mechanisms beyond the standard model (BSM), as predicted by models that involve the exchange of a non-SM mediator, such as a W boson or a charged Higgs boson [7]
This paper presents a search performed at the CMS experiment for single top quark production in the s channel considering the leptonic decay channels of the W boson produced in top quark decay
Summary
The central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter providing an axial magnetic field of 3.8 T. An electromagnetic calorimeter (ECAL) made of lead tungstate crystals and a brass and scintillator sampling hadron calorimeter, both arranged in a barrel assembly and two endcaps, surround the tracking volume and extend up to the region |η| < 3.0. Coverage up to |η| = 5.0 is provided by a quartz-fibre and steel absorber Cherenkov calorimeter. Muons are measured in gas-ionization detectors embedded in the steel flux-return yoke outside the solenoid. A more detailed description of the CMS detector, together with a definition of the coordinate system and the relevant kinematic variables, can be found in ref. A more detailed description of the CMS detector, together with a definition of the coordinate system and the relevant kinematic variables, can be found in ref. [9]
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