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Search for FCNC single top-quark production at √s = 7 TeV with the ATLAS detector

By G. Aad, H. M. Gray, Z. Marshall, D. Lopez Mateos and K. Perez

Abstract

A search for the production of single top-quarks via flavour-changing neutral-currents is presented. Data collected with the ATLAS detector at a centre-of-mass energy of √s = 7 TeV, corresponding to an integrated luminosity of 2.05 fb^(−1), are used. Candidate events with a semileptonic top-quark decay signature are classified as signal- or background-like events by using several kinematic variables as input to a neural network. No signal is observed in the neural network output distribution and a Bayesian upper limit is placed on the production cross-section. The observed upper limit at 95% confidence level on the cross-section multiplied by the t → W b branching fraction is measured to be σ_(qg→t)× B(t→Wb)<3.9 pb. This upper limit is converted using a model-independent approach into upper limits on the coupling strengths κ_(ugt)/Λ<6.9⋅10^(−3) TeV^(−1) and κ_(cgt)/Λ < 1.6⋅10^(−2) TeV^(−1), where Λ is the new physics scale, and on the branching fractions B(t → ug)<5.7⋅10^(−5) and B(t→cg)<2.7⋅10^(−4)

Publisher: 'Elsevier BV'
Year: 2012
OAI identifier: oai:authors.library.caltech.edu:32611

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