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Search for anomalous Wtb couplings and flavour-changing neutral currents in t-channel single top quark production in pp collisions at $\sqrt{s} =$ 7 and 8 TeV

The CMS collaboration
JHEP 1702 (2017) 028, 2017

Abstract (data abstract)
CERN-LHC. Limits on anomalous Wtb couplings and search for top quark flavour-changing neural currents using t-channel single top events from proton-proton collision data recorded in 2011 and 2012 with the CMS detector at the LHC at a centre-of-mass energy of 7 and 8 TeV with integrated luminocities of 5.0 and 19.7 /fb respectively and their combination. The final state is one muon and two or three jets. A Bayesian neural network technique, used to discriminate between the signal and backgrounds. The 95% confidence level (CL) exclusion limits on anomalous right-handed vector, and left- and right-handed tensor Wtb couplings are measured to be $|f_{RV}| < 0.16$, $|f_{LT}| < 0.057$, and $-0.049 < f_{RT} < 0.048$, respectively. For the FCNC couplings $\kappa_{tug}$ and $\kappa_{tcg}$, the 95% CL upper limits on coupling strengths are $|\kappa_{tug}|/\Lambda < 4.1 \times 10^{-3} TeV^{-1}$ and $|\kappa_{tcg}|/\Lambda < 1.8 \times 10^{-2} TeV^{-1}$, where $\Lambda$ is the scale for new physics, and correspond to upper limits on the branching fractions of $2.0 \times 10^{-5}$ and $4.1 \times 10^{-4}$ for the decays $t \rightarrow ug$ and $t \rightarrow cg$, respectively.

  • Table 1

    Data from Page 5 of paper, table 1


    Predicted and observed event yields before and after multijet BNN selection for $\sqrt{s}=7$ and $8$ TeV.

  • Table 2

    Data from Page 7 of paper, table 2


    List of input variables for the Bayesian neural networks used in the analysis. Numbers in the cells indicate whether the...

  • Table 3

    Data from Page 13 of paper, table 3


    One-dimensional exclusion limits on anomalous $Wtb$ couplings, evaluated in different two- and three-dimensional scenarios in the analyses conducted at $\sqrt{s}=7$...

  • Table 4

    Data from Page 15 of paper, table 4


    Observed and expected limits for the FCNC couplings at $\sqrt{s}=7$, $8$ TeV, and for combined $7+8$ TeV data.

  • Table 5

    Data from Page 15 of paper, table 4


    Observed and expected limits for the FCNC branching ratios at $\sqrt{s}=7$, $8$ TeV, and for combined $7+8$ TeV data.

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