Search for FCNC single top-quark production at √s=7 TeV with the ATLAS detector
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→Wb branching fraction is measured to be σqg→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−1 and κcgt/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.
Aad, G; Abbott, B; Abdallah, J; Abdelalim, AA; Abdesselam, A; Abdinov, O; Abi, B; Abolins, M; AbouZeid, OS; Abramowicz, H; Abreu, H; Acerbi, E; Acharya, BS; Adamczyk, L; Adams, DL; Addy, TN; Adelman, J; Aderholz, M; Adomeit, S; Adragna, P; Adye, T; Aefsky, S; Aguilar-Saavedra, JA; Aharrouche, M; Ahlen, SP; Ahles, F; Ahmad, A; Ahsan, M; Aielli, G; Akdogan, T; Åkesson, TPA; Akimoto, G; Akimov, AV; Akiyama, A; Alam, MS; Alam, MA; Albert, J; Albrand, S; Aleksa, M; Aleksandrov, IN; Alessandria, F; Alexa, C; Alexander, G; Alexandre, G; Alexopoulos, T; Alhroob, M; Aliev, M; Alimonti, G; Alison, J; Aliyev, M; Allbrooke, BMM; Allport, PP; Allwood-Spiers, SE; Almond, J; Aloisio, A; Alon, R; Alonso, A; Alvarez Gonzalez, B; Alviggi, MG; Amako, K; Amaral, P; Amelung, C; Ammosov, VV; Amorim, A; Amorós, G; Amram, N; Anastopoulos, C; Ancu, LS; Andari, N; Andeen, T; Anders, CF; Anders, G; Anderson, KJ; Andreazza, A; Andrei, V; Andrieux, ML; Anduaga, XS; Angerami, A; Anghinolfi, F; Anisenkov, A; Anjos, N; Annovi, A; Antonaki, A; Antonelli, M; Antonov, A; Antos, J; Anulli, F; Aoun, S; Aperio Bella, L; Apolle, R; Arabidze, G; Aracena, I; Arai, Y; Arce, ATH; Arfaoui, S; Arguin, JF; Arik, E; Arik, M; Armbruster, AJ; Arnaez, O
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