Study of heavy-flavor quarks produced in association with top-quark pairs at root s=7 TeV using the ATLAS detector

G. Aad; T. Abajyan; B. Abbott; J. Abdallah; S.A. Khalek; Mogens Dam; Jørgen Beck Hansen; Peter Henrik Hansen; Jørn Dines Hansen; John Renner Hansen; Nele Maria Philomena Boelaert; Esben Bryndt Klinkby; Sascha Mehlhase; Simon Johann Franz Heisterkamp; Ask Emil Løvschall-Jensen; Morten Dam Jørgensen; Troels Christian Petersen; Stefania Xella; Peter Kadlecik; Pavel Jez; Sune Jakobsen; Kristian Damlund Gregersen; James William Monk

doi:10.1103/PhysRevD.89.072012

Study of heavy-flavor quarks produced in association with top-quark pairs at root s=7 TeV using the ATLAS detector

G. Aad, T. Abajyan, B. Abbott, J. Abdallah, S.A. Khalek, Mogens Dam, Jørgen Beck Hansen, Peter Henrik Hansen, Jørn Dines Hansen, John Renner Hansen, Nele Maria Philomena Boelaert, Esben Bryndt Klinkby, Sascha Mehlhase, Simon Johann Franz Heisterkamp, Ask Emil Løvschall-Jensen, Morten Dam Jørgensen, Troels Christian Petersen, Stefania Xella, Peter Kadlecik, Pavel JezSune Jakobsen, Kristian Damlund Gregersen, James William Monk

Experimental Particle Physics

15 Citations (Scopus)

Abstract

Using a sample of dilepton top-quark pair (tt̄) candidate events, a study is performed of the production of top-quark pairs together with heavy-flavor (HF) quarks, the sum of tt̄+b+X and tt̄+c+X, collectively referred to as tt̄+HF. The data set used corresponds to an integrated luminosity of 4.7fb-1 of proton-proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. The presence of additional HF (b or c) quarks in the tt̄ sample is inferred by looking for events with at least three b-tagged jets, where two are attributed to the b quarks from the tt̄ decays and the third to additional HF production. The dominant background to tt̄+HF in this sample is tt̄+jet events in which a light-flavor jet is misidentified as a heavy-flavor jet. To determine the heavy- and light-flavor content of the additional b-tagged jets, a fit to the vertex mass distribution of b-tagged jets in the sample is performed. The result of the fit shows that 79±14(stat)±22(syst) of the 105 selected extra b-tagged jets originate from HF quarks, 3 standard deviations away from the hypothesis of zero tt̄+HF production. The result for extra HF production is quoted as a ratio (RHF) of the cross section for tt̄+HF production to the cross section for tt̄ production with at least one additional jet. Both cross sections are measured in a fiducial kinematic region within the ATLAS acceptance. RHF is measured to be [6.2±1.1(stat)±1.8(syst)]% for jets with pT>25GeV and |η|<2.5, in agreement with the expectations from Monte Carlo generators.

Original language	English
Article number	072012
Journal	Physical Review D (Particles, Fields, Gravitation and Cosmology)
Volume	89
Issue number	7
ISSN	1550-7998
DOIs	https://doi.org/10.1103/PhysRevD.89.072012
Publication status	Published - 21 Apr 2014

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Aad, G., Abajyan, T., Abbott, B., Abdallah, J., Khalek, S. A., Dam, M., Hansen, J. B., Hansen, P. H., Hansen, J. D., Hansen, J. R., Boelaert, N. M. P., Klinkby, E. B., Mehlhase, S., Heisterkamp, S. J. F., Løvschall-Jensen, A. E., Jørgensen, M. D., Petersen, T. C., Xella, S., Kadlecik, P., ... Monk, J. W. (2014). Study of heavy-flavor quarks produced in association with top-quark pairs at root s=7 TeV using the ATLAS detector. Physical Review D (Particles, Fields, Gravitation and Cosmology), 89(7), Article 072012. https://doi.org/10.1103/PhysRevD.89.072012

Aad, G, Abajyan, T, Abbott, B, Abdallah, J, Khalek, SA, Dam, M , Hansen, JB , Hansen, PH , Hansen, JD , Hansen, JR, Boelaert, NMP, Klinkby, EB, Mehlhase, S, Heisterkamp, SJF, Løvschall-Jensen, AE, Jørgensen, MD, Petersen, TC , Xella, S, Kadlecik, P, Jez, P, Jakobsen, S, Gregersen, KD & Monk, JW 2014, 'Study of heavy-flavor quarks produced in association with top-quark pairs at root s=7 TeV using the ATLAS detector', Physical Review D (Particles, Fields, Gravitation and Cosmology), vol. 89, no. 7, 072012. https://doi.org/10.1103/PhysRevD.89.072012

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title = "Study of heavy-flavor quarks produced in association with top-quark pairs at root s=7 TeV using the ATLAS detector",

abstract = "Using a sample of dilepton top-quark pair (t{\=t}) candidate events, a study is performed of the production of top-quark pairs together with heavy-flavor (HF) quarks, the sum of t{\=t}+b+X and t{\=t}+c+X, collectively referred to as t{\=t}+HF. The data set used corresponds to an integrated luminosity of 4.7fb-1 of proton-proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. The presence of additional HF (b or c) quarks in the t{\=t} sample is inferred by looking for events with at least three b-tagged jets, where two are attributed to the b quarks from the t{\=t} decays and the third to additional HF production. The dominant background to t{\=t}+HF in this sample is t{\=t}+jet events in which a light-flavor jet is misidentified as a heavy-flavor jet. To determine the heavy- and light-flavor content of the additional b-tagged jets, a fit to the vertex mass distribution of b-tagged jets in the sample is performed. The result of the fit shows that 79±14(stat)±22(syst) of the 105 selected extra b-tagged jets originate from HF quarks, 3 standard deviations away from the hypothesis of zero t{\=t}+HF production. The result for extra HF production is quoted as a ratio (RHF) of the cross section for t{\=t}+HF production to the cross section for t{\=t} production with at least one additional jet. Both cross sections are measured in a fiducial kinematic region within the ATLAS acceptance. RHF is measured to be [6.2±1.1(stat)±1.8(syst)]% for jets with pT>25GeV and |η|<2.5, in agreement with the expectations from Monte Carlo generators.",

author = "G. Aad and T. Abajyan and B. Abbott and J. Abdallah and S.A. Khalek and Mogens Dam and Hansen, {J{\o}rgen Beck} and Hansen, {Peter Henrik} and Hansen, {J{\o}rn Dines} and Hansen, {John Renner} and Boelaert, {Nele Maria Philomena} and Klinkby, {Esben Bryndt} and Sascha Mehlhase and Heisterkamp, {Simon Johann Franz} and L{\o}vschall-Jensen, {Ask Emil} and J{\o}rgensen, {Morten Dam} and Petersen, {Troels Christian} and Stefania Xella and Peter Kadlecik and Pavel Jez and Sune Jakobsen and Gregersen, {Kristian Damlund} and Monk, {James William}",

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doi = "10.1103/PhysRevD.89.072012",

language = "English",

volume = "89",

journal = "Physical Review D (Particles, Fields, Gravitation and Cosmology)",

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TY - JOUR

T1 - Study of heavy-flavor quarks produced in association with top-quark pairs at root s=7 TeV using the ATLAS detector

AU - Aad, G.

AU - Abajyan, T.

AU - Abbott, B.

AU - Abdallah, J.

AU - Khalek, S.A.

AU - Dam, Mogens

AU - Hansen, Jørgen Beck

AU - Hansen, Peter Henrik

AU - Hansen, Jørn Dines

AU - Hansen, John Renner

AU - Boelaert, Nele Maria Philomena

AU - Klinkby, Esben Bryndt

AU - Mehlhase, Sascha

AU - Heisterkamp, Simon Johann Franz

AU - Løvschall-Jensen, Ask Emil

AU - Jørgensen, Morten Dam

AU - Petersen, Troels Christian

AU - Xella, Stefania

AU - Kadlecik, Peter

AU - Jez, Pavel

AU - Jakobsen, Sune

AU - Gregersen, Kristian Damlund

AU - Monk, James William

PY - 2014/4/21

Y1 - 2014/4/21

N2 - Using a sample of dilepton top-quark pair (tt̄) candidate events, a study is performed of the production of top-quark pairs together with heavy-flavor (HF) quarks, the sum of tt̄+b+X and tt̄+c+X, collectively referred to as tt̄+HF. The data set used corresponds to an integrated luminosity of 4.7fb-1 of proton-proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. The presence of additional HF (b or c) quarks in the tt̄ sample is inferred by looking for events with at least three b-tagged jets, where two are attributed to the b quarks from the tt̄ decays and the third to additional HF production. The dominant background to tt̄+HF in this sample is tt̄+jet events in which a light-flavor jet is misidentified as a heavy-flavor jet. To determine the heavy- and light-flavor content of the additional b-tagged jets, a fit to the vertex mass distribution of b-tagged jets in the sample is performed. The result of the fit shows that 79±14(stat)±22(syst) of the 105 selected extra b-tagged jets originate from HF quarks, 3 standard deviations away from the hypothesis of zero tt̄+HF production. The result for extra HF production is quoted as a ratio (RHF) of the cross section for tt̄+HF production to the cross section for tt̄ production with at least one additional jet. Both cross sections are measured in a fiducial kinematic region within the ATLAS acceptance. RHF is measured to be [6.2±1.1(stat)±1.8(syst)]% for jets with pT>25GeV and |η|<2.5, in agreement with the expectations from Monte Carlo generators.

AB - Using a sample of dilepton top-quark pair (tt̄) candidate events, a study is performed of the production of top-quark pairs together with heavy-flavor (HF) quarks, the sum of tt̄+b+X and tt̄+c+X, collectively referred to as tt̄+HF. The data set used corresponds to an integrated luminosity of 4.7fb-1 of proton-proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. The presence of additional HF (b or c) quarks in the tt̄ sample is inferred by looking for events with at least three b-tagged jets, where two are attributed to the b quarks from the tt̄ decays and the third to additional HF production. The dominant background to tt̄+HF in this sample is tt̄+jet events in which a light-flavor jet is misidentified as a heavy-flavor jet. To determine the heavy- and light-flavor content of the additional b-tagged jets, a fit to the vertex mass distribution of b-tagged jets in the sample is performed. The result of the fit shows that 79±14(stat)±22(syst) of the 105 selected extra b-tagged jets originate from HF quarks, 3 standard deviations away from the hypothesis of zero tt̄+HF production. The result for extra HF production is quoted as a ratio (RHF) of the cross section for tt̄+HF production to the cross section for tt̄ production with at least one additional jet. Both cross sections are measured in a fiducial kinematic region within the ATLAS acceptance. RHF is measured to be [6.2±1.1(stat)±1.8(syst)]% for jets with pT>25GeV and |η|<2.5, in agreement with the expectations from Monte Carlo generators.

U2 - 10.1103/PhysRevD.89.072012

DO - 10.1103/PhysRevD.89.072012

M3 - Journal article

SN - 1550-7998

VL - 89

JO - Physical Review D (Particles, Fields, Gravitation and Cosmology)

JF - Physical Review D (Particles, Fields, Gravitation and Cosmology)

IS - 7

M1 - 072012

ER -

Study of heavy-flavor quarks produced in association with top-quark pairs at root s=7 TeV using the ATLAS detector

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