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 8TeV 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 sigma(qg -> t) x B(t -> Wb) < 3.4 pb and the expected 95% CL limit is sigma(qg -> t) x B(t -> Wb) < 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 x 10(-3) TeV-1 and kappa(cgt)/Lambda < 13x10(-3) TeV and on the branching fractions B(t -> ug) < 4.0 x 10(-5) and B(t -> cg) < 20 x 10(-5).

Search for single top-quark production via flavour-changing neutral currents at 8TeV with the ATLAS detector / Iuppa, Roberto; Atlas, Collaboration. - In: THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS. - ISSN 1434-6044. - 76:2(2016), pp. 5501-5530. [10.1140/epjc/s10052-016-3876-4]

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

Iuppa, Roberto;
2016

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 8TeV 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 sigma(qg -> t) x B(t -> Wb) < 3.4 pb and the expected 95% CL limit is sigma(qg -> t) x B(t -> Wb) < 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 x 10(-3) TeV-1 and kappa(cgt)/Lambda < 13x10(-3) TeV and on the branching fractions B(t -> ug) < 4.0 x 10(-5) and B(t -> cg) < 20 x 10(-5).
2
Iuppa, Roberto; Atlas, Collaboration
Search for single top-quark production via flavour-changing neutral currents at 8TeV with the ATLAS detector / Iuppa, Roberto; Atlas, Collaboration. - In: THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS. - ISSN 1434-6044. - 76:2(2016), pp. 5501-5530. [10.1140/epjc/s10052-016-3876-4]
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11572/162977
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