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Title

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

CollaborationWith : Abdelalim Aly, Ahmed Aly / Alexandre, Gauthier / Backes, Moritz / Barone, Gaetano / Bell, Paul / Bell, William / Benhar Noccioli, Eleonora / Blondel, Alain / Bucci, Francesca / Clark, Allan Geoffrey / Dao, Valerio / Doglioni, Caterina / Ferrere, Didier / Gadomski, Szymon / Gonzalez Sevilla, Sergio / Goulette, Marc / Iacobucci, Giuseppe / La Rosa, Alessandro / Leger, Annie / Lister, Alison / Martin Dit Latour, Bertrand / Mermod, Philippe / Mora Herrera, Maria Clemencia Rosario / Nektarijevic, Snezana / Nikolics, Katalin / Pasztor, Arpad / Pohl, Martin / Rosbach, Kilian / Rosselet, Laurent / Wu, Xin
Published in Physics Letters. B. 2012, vol. 718, no. 4-5, p. 351-369
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→Wbt→Wb branching fraction is measured to be σqg→t×B(t→Wb)<3.9 pbσqg→t×B(t→Wb)<3.9 pb. This upper limit is converted using a model-independent approach into upper limits on the coupling strengths κugt/Λ<6.9⋅10−3 TeV−1κugt/Λ<6.9⋅10−3 TeV−1 and κcgt/Λ<1.6⋅10−2 TeV−1κcgt/Λ<1.6⋅10−2 TeV−1, where Λ is the new physics scale, and on the branching fractions B(t→ug)<5.7⋅10−5B(t→ug)<5.7⋅10−5 and B(t→cg)<2.7⋅10−4B(t→cg)<2.7⋅10−4.
Keywords Top physicsHeavy-quark productionFCNCSingle top quark
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ATLAS COLLABORATION. Search for FCNC single top-quark production at √s=7 TeV with the ATLAS detector. In: Physics Letters. B, 2012, vol. 718, n° 4-5, p. 351-369. https://archive-ouverte.unige.ch/unige:40256

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Deposited on : 2014-09-18

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