Search for single top-quark production via flavour-changing neutral currents at 8 TeV with the ATLAS detector

0470769 - FZÚ 2017 RIV US eng J - Journal Article
Aad, G. - Abbott, B. - Abdallah, J. - Chudoba, Jiří - Havránek, Miroslav - Hejbal, Jiří - Jakoubek, Tomáš - Kepka, Oldřich - Kupčo, Alexander - Kůs, Vlastimil - Lokajíček, Miloš - Lysák, Roman - Marčišovský, Michal - Mikeštíková, Marcela - Němeček, Stanislav - Penc, Ondřej - Šícho, Petr - Staroba, Pavel - Svatoš, Michal - Taševský, Marek - Vrba, Václav … Total 2857 authors
Search for single top-quark production via flavour-changing neutral currents at 8 TeV with the ATLAS detector.
European Physical Journal C. Roč. 76, č. 2 (2016), s. 1-29, č. článku 55. ISSN 1434-6044. E-ISSN 1434-6052
Institutional support: RVO:68378271
Keywords : ATLAS * neural network * CERN LHC Coll * initial state * new physics
Subject RIV: BF - Elementary Particles and High Energy Physics
Impact factor: 5.297, year: 2016

A search for single top-quark production via flavour-changing neutral current processes from gluon plus up- or charm-quark initial states in proton–proton collisions at the LHC is presented. Data collected with the ATLAS detector in 2012 at a centre-of-mass energy of 8 TeV and corresponding to an integrated luminosity of 20.3 fb−1 are used. Candidate events for a top quark decaying into a lepton, a neutrino and a jet are selected and classified into signal- and background-like candidates using a neural network. No signal is observed and an upper limit on the production cross-section multiplied by the t→Wb branching fraction is set. The observed 95 % CL limit is σqg→t×B(t→Wb)<3.4pb and the expected 95 % CL limit is σqg→t×B(t→Wb)<2.9pb . The observed limit can be interpreted as upper limits on the coupling constants of the flavour-changing neutral current interactions divided by the scale of new physics κugt/Λ<5.8×10−3TeV−1 and κcgt/Λ<13×10−3TeV and on the branching fractions B(t→ug)<4.0×10−5 and B(t→cg)<20×10−5 .

Permanent Link: http://hdl.handle.net/11104/0268333