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

G. Aad; Mogens Dam; Nele Maria Philomena Boelaert; Jørgen Beck Hansen; Peter Henrik Hansen; John Renner Hansen; Jørn Dines Hansen; Simon Johann Franz Heisterkamp; Morten Dam Jørgensen; Esben Bryndt Klinkby; Sascha Mehlhase; Björn Stefan Nilsson; Troels Christian Petersen; Stefania Xella; Ask Emil Løvschall-Jensen

doi:10.1016/j.physletb.2012.05.022

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

G. Aad, Mogens Dam, Nele Maria Philomena Boelaert, Jørgen Beck Hansen, Peter Henrik Hansen, John Renner Hansen, Jørn Dines Hansen, Simon Johann Franz Heisterkamp, Morten Dam Jørgensen, Esben Bryndt Klinkby, Sascha Mehlhase, Björn Stefan Nilsson, Troels Christian Petersen, Stefania Xella, Ask Emil Løvschall-Jensen

57 Citations (Scopus)

Abstract

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 σ_qg→t×B(t→Wb)<3.9 pb. This upper limit is converted using a model-independent approach into upper limits on the coupling strengths κ_ugt/Λ<6.9⋅10⁻³ TeV⁻¹ and κ_cgt/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.

Original language	English
Journal	Physics Letters B
Volume	712
Issue number	4-5
Pages (from-to)	351-369
ISSN	0370-2693
DOIs	https://doi.org/10.1016/j.physletb.2012.05.022
Publication status	Published - 12 Jun 2012

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Aad, G., Dam, M., Boelaert, N. M. P., Hansen, J. B., Hansen, P. H., Hansen, J. R., Hansen, J. D., Heisterkamp, S. J. F., Jørgensen, M. D., Klinkby, E. B., Mehlhase, S., Nilsson, B. S., Petersen, T. C., Xella, S., & Løvschall-Jensen, A. E. (2012). Search for FCNC single top-quark production at sqrt(s) = 7 TeV with the ATLAS detector. Physics Letters B, 712(4-5), 351-369. https://doi.org/10.1016/j.physletb.2012.05.022

Aad, G, Dam, M, Boelaert, NMP, Hansen, JB , Hansen, PH , Hansen, JR , Hansen, JD, Heisterkamp, SJF, Jørgensen, MD, Klinkby, EB, Mehlhase, S, Nilsson, BS, Petersen, TC , Xella, S & Løvschall-Jensen, AE 2012, 'Search for FCNC single top-quark production at sqrt(s) = 7 TeV with the ATLAS detector', Physics Letters B, vol. 712, no. 4-5, pp. 351-369. https://doi.org/10.1016/j.physletb.2012.05.022

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title = "Search for FCNC single top-quark production at sqrt(s) = 7 TeV with the ATLAS detector",

abstract = "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.",

author = "G. Aad and Mogens Dam and Boelaert, {Nele Maria Philomena} and Hansen, {J{\o}rgen Beck} and Hansen, {Peter Henrik} and Hansen, {John Renner} and Hansen, {J{\o}rn Dines} and Heisterkamp, {Simon Johann Franz} and J{\o}rgensen, {Morten Dam} and Klinkby, {Esben Bryndt} and Sascha Mehlhase and Nilsson, {Bj{\"o}rn Stefan} and Petersen, {Troels Christian} and Stefania Xella and L{\o}vschall-Jensen, {Ask Emil}",

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doi = "10.1016/j.physletb.2012.05.022",

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T1 - Search for FCNC single top-quark production at sqrt(s) = 7 TeV with the ATLAS detector

AU - Aad, G.

AU - Dam, Mogens

AU - Boelaert, Nele Maria Philomena

AU - Hansen, Jørgen Beck

AU - Hansen, Peter Henrik

AU - Hansen, John Renner

AU - Hansen, Jørn Dines

AU - Heisterkamp, Simon Johann Franz

AU - Jørgensen, Morten Dam

AU - Klinkby, Esben Bryndt

AU - Mehlhase, Sascha

AU - Nilsson, Björn Stefan

AU - Petersen, Troels Christian

AU - Xella, Stefania

AU - Løvschall-Jensen, Ask Emil

PY - 2012/6/12

Y1 - 2012/6/12

N2 - 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.

AB - 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.

U2 - 10.1016/j.physletb.2012.05.022

DO - 10.1016/j.physletb.2012.05.022

M3 - Journal article

SN - 0370-2693

VL - 712

SP - 351

EP - 369

JO - Physics Letters B: Particle Physics, Nuclear Physics and Cosmology

JF - Physics Letters B: Particle Physics, Nuclear Physics and Cosmology

IS - 4-5

ER -

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

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