CMS-PAS-TOP-14-007

CMS-PAS-TOP-14-007
Search for anomalous Wtb couplings and top FCNC in t-channel single-top-quark events
CMS Collaboration
2014

Abstract: Single-top-quark events in the $t$ -channel are used to probe Wtb anomalous couplings and to search for top quark Flavor Changing Neutral Current (FCNC) interactions in proton-proton collisions at $\sqrt{s}=7$ TeV. The analyzed data correspond to an integrated luminosity of 5~fb $^{-1}$ . Events with the top quark decaying into a muon, neutrino and b-quark are selected. A Bayesian neural network is used to discriminate between signal and backgrounds. The observed event yields are consistent with SM prediction, and exclusion limits at 95\% C.L. are determined. The exclusion limits on anomalous right vector and left tensor couplings of the Wtb vertex are found to be $\|f_{V}^{R}\|< 0.34$ and $\|f_{T}^{L}\|<0.09$ . In the scenarios with FCNC tcg and tug couplings, limits on the coupling strengths are found to be $\kappa_{tug}/\Lambda < 1.8 \cdot 10^{-2}~ \mathrm{TeV^{-1}},\ \kappa_{tcg}/\Lambda < 5.6 \cdot 10^{-2} ~ \mathrm{TeV^{-1}}$ which corresponds to limits on the branching ratios $Br(t~\rightarrow~u+g)~<~3.55\times10^{-4},\ Br(t~\rightarrow~c+g)~<~3.44\times10^{-3}$ .
Links: CDS record (PDF) ; inSPIRE record ; Public twiki page ; CADI line (restricted) ; These preliminary results are superseded in this paper, JHEP 02 (2017) 028. The superseded preliminary plots can be found here.

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