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

Aad G., Abbott B., Abdallah J., Abdelalim A. A. , Abdesselam A., Abdinov O., ...More

PHYSICS LETTERS B, vol.712, pp.351-369, 2012 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 712
  • Publication Date: 2012
  • Doi Number: 10.1016/j.physletb.2012.05.022
  • Title of Journal : PHYSICS LETTERS B
  • Page Numbers: pp.351-369
  • Keywords: Top physics, Heavy-quark production, FCNC, Single top quark, CHANGING NEUTRAL CURRENTS, HADRON COLLIDERS, FLAVOR, DECAYS


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 root 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 -> Wb branching fraction is measured to be sigma(qg -> t) x B(t -> Wb) < 3.9 pb. This upper limit is converted using a model-independent approach into upper limits on the coupling strengths kappa(ugt)/Lambda < 6.9.10(-3) TeV-1 and kappa(cgt)/Lambda < 1.6.10(-2) TeV-1, where A 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). (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.