In:
The European Physical Journal C, Springer Science and Business Media LLC, Vol. 76, No. 2 ( 2016-02)
Abstract:
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 $$^{-1}$$ - 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 $$t \rightarrow Wb$$ t → W b branching fraction is set. The observed 95 % CL limit is $$\sigma _{qg \rightarrow t} {\,\times \,} \mathcal {B}(t \rightarrow Wb) 〈 {3.4}\,\mathrm{pb}$$ σ q g → t × B ( t → W b ) 〈 3.4 pb and the expected 95 % CL limit is $$\sigma _{qg \rightarrow t} \times \mathcal {B}(t \rightarrow Wb) 〈 {2.9}\,\mathrm{pb}$$ σ q g → t × B ( t → W b ) 〈 2.9 pb . 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 $$\kappa _{ugt}/\Lambda 〈 5.8 \times 10^{-3}\, \mathrm{TeV}^{-1}$$ κ u g t / Λ 〈 5.8 × 10 - 3 TeV - 1 and $$\kappa _{cgt}/\Lambda 〈 13 \times 10^{-3}\, \mathrm{TeV}$$ κ c g t / Λ 〈 13 × 10 - 3 TeV and on the branching fractions $$\mathcal {B}(t \rightarrow ug) 〈 {4.0 \times 10^{-5}}$$ B ( t → u g ) 〈 4.0 × 10 - 5 and $$\mathcal {B}(t \rightarrow cg) 〈 {20 \times 10^{-5}}$$ B ( t → c g ) 〈 20 × 10 - 5 .
Type of Medium:
Online Resource
ISSN:
1434-6044
,
1434-6052
DOI:
10.1140/epjc/s10052-016-3876-4
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
2016
detail.hit.zdb_id:
1397769-6
detail.hit.zdb_id:
1459069-4
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