Compact Muon Solenoid
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| CMS-PAS-TOP-25-015 | ||
| Search for top quark FCNCs in multilepton final states using an effective field theory approach in proton-proton collisions at $ \sqrt{s}= $ 13 TeV | ||
| CMS Collaboration | ||
| 2026-05-22 | ||
| Abstract: We present a search for flavour-changing neutral current (FCNC) interactions involving the top quark in production and decay. This analysis establishes the first global search in the top-quark FCNC sector within the standard model effective field theory where all relevant operators are constrained simultaneously in a single fit to data, providing a framework for future measurements and combinations at the LHC. The analysis uses proton--proton collision data at $ \sqrt{s}= $ 13 TeV, corresponding to an integrated luminosity of 138 fb$ ^{-1} $. Signal contributions are probed in final states with two same-sign leptons or three leptons. Multivariate discriminants are used to separate signal from background, and their distributions enter a likelihood fit to determine 95% confidence intervals for 24 Wilson coefficients. No evidence for FCNC interactions is observed. The results provide the first simultaneous constraints on the complete operator set and set the most stringent limits to date on FCNC top-quark decay branching fractions via two-lepton-two-quark interactions, $ \mathrm{BR}(\mathrm{t}\to \ell^{+}\ell^{-}\mathrm{q}) $, where $ \mathrm{q}=\mathrm{u} $ or c. | ||
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Links:
CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, Submitted to PRL. The superseded preliminary plots can be found here. |
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Compact Muon Solenoid LHC, CERN |
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