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  • 1
    Online Resource
    Online Resource
    Combination of inclusive top-quark pair production cross-section measurements using ATLAS and CMS data at $$ \sqrt{s} $$ = 7 and 8 TeV
    Springer Science and Business Media LLC ; 2023
    In:  Journal of High Energy Physics Vol. 2023, No. 7 ( 2023-07-27)
    Details
    In: Journal of High Energy Physics, Springer Science and Business Media LLC, Vol. 2023, No. 7 ( 2023-07-27)
    Abstract: A combination of measurements of the inclusive top-quark pair production cross-section performed by ATLAS and CMS in proton–proton collisions at centre-of-mass energies of 7 and 8 TeV at the LHC is presented. The cross-sections are obtained using top-quark pair decays with an opposite-charge electron–muon pair in the final state and with data corresponding to an integrated luminosity of about 5 fb − 1 at $$ \sqrt{s} $$ s = 7 TeV and about 20 fb − 1 at $$ \sqrt{s} $$ s = 8 TeV for each experiment. The combined cross-sections are determined to be 178 . 5 ± 4 . 7 pb at $$ \sqrt{s} $$ s = 7 TeV and $$ {243.3}_{-5.9}^{+6.0} $$ 243.3 − 5.9 + 6.0 pb at $$ \sqrt{s} $$ s = 8 TeV with a correlation of 0.41, using a reference top-quark mass value of 172.5 GeV. The ratio of the combined cross-sections is determined to be R 8 / 7 = 1 . 363 ± 0 . 032. The combined measured cross-sections and their ratio agree well with theory calculations using several parton distribution function (PDF) sets. The values of the top-quark pole mass (with the strong coupling fixed at 0.118) and the strong coupling (with the top-quark pole mass fixed at 172.5 GeV) are extracted from the combined results by fitting a next-to-next-to-leading-order plus next-to-next-to-leading-log QCD prediction to the measurements. Using a version of the NNPDF3.1 PDF set containing no top-quark measurements, the results obtained are $$ {m}_t^{\textrm{pole}}={173.4}_{-2.0}^{+1.8} $$ m t pole = 173.4 − 2.0 + 1.8 GeV and $$ {\alpha}_{\textrm{s}}\left({m}_Z\right)={0.1170}_{-0.0018}^{+0.0021} $$ α s m Z = 0.1170 − 0.0018 + 0.0021 .
    Type of Medium: Online Resource
    ISSN: 1029-8479
    URL: Article
    DOI: 10.1007/JHEP07(2023)213
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2023
    detail.hit.zdb_id: 2027350-2
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  • 2
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    Online Resource
    The ATLAS Fast TracKer system
    IOP Publishing ; 2021
    In:  Journal of Instrumentation Vol. 16, No. 07 ( 2021-07-01), p. P07006-
    Details
    In: Journal of Instrumentation, IOP Publishing, Vol. 16, No. 07 ( 2021-07-01), p. P07006-
    Abstract: The ATLAS Fast TracKer (FTK) was designed to provide full tracking for the ATLAS high-level trigger by using pattern recognition based on Associative Memory (AM) chips and fitting in high-speed field programmable gate arrays. The tracks found by the FTK are based on inputs from all modules of the pixel and silicon microstrip trackers. The as-built FTK system and components are described, as is the online software used to control them while running in the ATLAS data acquisition system. Also described is the simulation of the FTK hardware and the optimization of the AM pattern banks. An optimization for long-lived particles with large impact parameter values is included. A test of the FTK system with the data playback facility that allowed the FTK to be commissioned during the shutdown between Run 2 and Run 3 of the LHC is reported. The resulting tracks from part of the FTK system covering a limited η–ϕ region of the detector are compared with the output from the FTK simulation. It is shown that FTK performance is in good agreement with the simulation.
    Type of Medium: Online Resource
    ISSN: 1748-0221
    URL: Article
    DOI: 10.1088/1748-0221/16/07/P07006
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 2235672-1
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  • 3
    Online Resource
    Online Resource
    Combinations of single-top-quark production cross-section measurements and |fLVVtb| determinations at $$ \sqrt{s} $$ = 7 and 8 TeV with the ATLAS and CMS experiments
    Springer Science and Business Media LLC ; 2019
    In:  Journal of High Energy Physics Vol. 2019, No. 5 ( 2019-05)
    Details
    In: Journal of High Energy Physics, Springer Science and Business Media LLC, Vol. 2019, No. 5 ( 2019-05)
    Abstract: This paper presents the combinations of single-top-quark production cross-section measurements by the ATLAS and CMS Collaborations, using data from LHC proton-proton collisions at $$ \sqrt{s} $$ s = 7 and 8 TeV corresponding to integrated luminosities of 1.17 to 5.1 fb −1 at $$ \sqrt{s} $$ s = 7 TeV and 12.2 to 20.3 fb −1 at $$ \sqrt{s} $$ s = 8 TeV. These combinations are performed per centre-of-mass energy and for each production mode: t -channel, tW , and s -channel. The combined t -channel cross-sections are 67.5 ± 5.7 pb and 87.7 ± 5.8 pb at $$ \sqrt{s} $$ s = 7 and 8 TeV respectively. The combined tW cross-sections are 16.3 ± 4.1 pb and 23.1 ± 3.6 pb at $$ \sqrt{s} $$ s = 7 and 8 TeV respectively. For the s -channel cross-section, the combination yields 4.9 ± 1.4 pb at $$ \sqrt{s} $$ s = 8 TeV. The square of the magnitude of the CKM matrix element V tb multiplied by a form factor f LV is determined for each production mode and centre-of-mass energy, using the ratio of the measured cross-section to its theoretical prediction. It is assumed that the top-quark-related CKM matrix elements obey the relation | V td |, | V ts | ≪ | V tb |. All the | f LV V tb | 2 determinations, extracted from individual ratios at $$ \sqrt{s} $$ s = 7 and 8 TeV, are combined, resulting in | f LV V tb | = 1.02 ± 0.04 (meas.) ± 0.02 (theo.). All combined measurements are consistent with their corresponding Standard Model predictions.
    Type of Medium: Online Resource
    ISSN: 1029-8479
    URL: Article
    DOI: 10.1007/JHEP05(2019)088
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2019
    detail.hit.zdb_id: 2027350-2
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  • 4
    Online Resource
    Online Resource
    Combination of the W boson polarization measurements in top quark decays using ATLAS and CMS data at $$ \sqrt{s} $$ = 8 TeV
    Springer Science and Business Media LLC ; 2020
    In:  Journal of High Energy Physics Vol. 2020, No. 8 ( 2020-08)
    Details
    In: Journal of High Energy Physics, Springer Science and Business Media LLC, Vol. 2020, No. 8 ( 2020-08)
    Abstract: The combination of measurements of the W boson polarization in top quark decays performed by the ATLAS and CMS collaborations is presented. The measurements are based on proton-proton collision data produced at the LHC at a centre-of-mass energy of 8 TeV, and corresponding to an integrated luminosity of about 20 fb − 1 for each experiment. The measurements used events containing one lepton and having different jet multiplicities in the final state. The results are quoted as fractions of W bosons with longitudinal ( F 0 ), left-handed ( F L ), or right-handed ( F R ) polarizations. The resulting combined measurements of the polarization fractions are F 0 = 0 . 693 ± 0 . 014 and F L = 0 . 315 ± 0 . 011. The fraction F R is calculated from the unitarity constraint to be F R = − 0 . 008 ± 0 . 007. These results are in agreement with the standard model predictions at next-to-next-to-leading order in perturbative quantum chromodynamics and represent an improvement in precision of 25 (29)% for F 0 ( F L ) with respect to the most precise single measurement. A limit on anomalous right-handed vector ( V R ), and left- and right-handed tensor ( g L , g R ) tWb couplings is set while fixing all others to their standard model values. The allowed regions are [ − 0 . 11 , 0 . 16] for V R , [ − 0 . 08 , 0 . 05] for g L , and [ − 0 . 04 , 0 . 02] for g R , at 95% confidence level. Limits on the corresponding Wilson coefficients are also derived.
    Type of Medium: Online Resource
    ISSN: 1029-8479
    URL: Article
    DOI: 10.1007/JHEP08(2020)051
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2020
    detail.hit.zdb_id: 2027350-2
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