著者

原 和彦 金 信弘 大川 英希 佐藤 構二 受川 史彦 ATLAS Collaboration Hara K. Kim S.H. Okawa H. Sato K. Ukegawa F.

出版者

Elsevier B.V.

雑誌

Physics letters. B (ISSN:03702693)

巻号頁・発行日

no.759, pp.601-621, 2016-08

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Measurements of the W±→ℓ±ν and Z→ℓ+ℓ− production cross sections (where ℓ±=e±,μ±) in proton–proton collisions at √s=13 TeV are presented using data recorded by the ATLAS experiment at the Large Hadron Collider, corresponding to a total integrated luminosity of 81 pb−1. The total inclusive W±-boson production cross sections times the single-lepton-flavour branching ratios are σtotW+=11.83 ±0.02(stat)±0.32(sys)±0.25 (lumi) nb and σtotW−=8.79 ±0.02(stat)±0.24(sys)±0.18 (lumi) nb for W+ and W−, respectively. The total inclusive Z -boson production cross section times leptonic branching ratio, within the invariant mass window 66<mℓℓ<116 GeV, is σtotZ=1.981 ±0.007(stat)±0.038(sys)±0.042 (lumi) nb. The W+, W−, and Z -boson production cross sections and cross-section ratios within a fiducial region defined by the detector acceptance are also measured. The cross-section ratios benefit from significant cancellation of experimental uncertainties, resulting in σfidW+/σfidW−=1.295 ±0.003(stat)±0.010 (sys) and σfidW±/σfidZ=10.31 ±0.04(stat)±0.20 (sys). Theoretical predictions, based on calculations accurate to next-to-next-to-leading order for quantum chromodynamics and to next-to-leading order for electroweak processes and which employ different parton distribution function sets, are compared to these measurements.

著者

原 和彦 佐藤 構二 受川 史彦 ATLAS Collaboration

出版者

Springer

雑誌

The European physical journal. C (ISSN:14346044)

巻号頁・発行日

vol.80, no.8, 2020-08

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The results of a search for electroweakino pair production pp→χ~±1χ~02 in which the chargino (χ~±1) decays into a W boson and the lightest neutralino (χ~01), while the heavier neutralino (χ~02) decays into the Standard Model 125 GeV Higgs boson and a second χ~01 are presented. The signal selection requires a pair of b-tagged jets consistent with those from a Higgs boson decay, and either an electron or a muon from the W boson decay, together with missing transverse momentum from the corresponding neutrino and the stable neutralinos. The analysis is based on data corresponding to 139 fb−1 of s√=13 TeV pp collisions provided by the Large Hadron Collider and recorded by the ATLAS detector. No statistically significant evidence of an excess of events above the Standard Model expectation is found. Limits are set on the direct production of the electroweakinos in simplified models, assuming pure wino cross-sections. Masses of χ~±1/χ~02 up to 740 GeV are excluded at 95% confidence level for a massless χ~01.

著者

原 和彦 金 信弘 大川 英希 佐藤 構二 受川 史彦 ATLAS Collaboration Hara K. Kim S.H. Okawa H. Sato K. Ukegawa F.

出版者

American Physical Society

雑誌

Physical Review D (ISSN:24700010)

巻号頁・発行日

vol.97, no.5, 2018-03-27

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A search for electroweak production of supersymmetric particles in scenarios with compressed mass spectra in final states with two low-momentum leptons and missing transverse momentum is presented. This search uses proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2015-2016, corresponding to 36.1 tb(-1) of integrated luminosity at root s = 13 TeV. Events with same flavor pairs of electrons or muons with opposite electric charge are selected. The data are found to be consistent with the Standard Model prediction. Results are interpreted using simplified models of R-parity conserving supersymmetry in which there is a small mass difference between the masses of the produced supersymmetric particles and the lightest neutralino. Exclusion limits at 95% confidence level are set on next-to-lightest neutralino masses of up to 145 GeV for Higgsino production and 175 GeV for wino production, and slepton masses of up to 190 GeV for pair production of sleptons. In the compressed mass regime, the exclusion limits extend down to mass splittings of 2.5 GeV for Higgsino production, 2 GeV for wino production, and 1 GeV for slepton production. The results are also interpreted in the context of a radiatively-driven natural supersymmetry model with nonuniversal Higgs boson masses.

著者

原 和彦 金 信弘 大川 英希 佐藤 構二 受川 史彦 ATLAS Collaboration Hara K. Kim S.H. Okawa H. Sato K. Ukegawa F.

出版者

Springer

雑誌

Journal of high energy physics (ISSN:10298479)

巻号頁・発行日

vol.2018, no.6, 2018-06

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This paper presents a search for direct electroweak gaugino or gluino pair production with a chargino nearly mass-degenerate with a stable neutralino. It is based on an integrated luminosity of 36.1 fb−1 of pp collisions at s√=13 TeV collected by the ATLAS experiment at the LHC. The final state of interest is a disappearing track accompanied by at least one jet with high transverse momentum from initial-state radiation or by four jets from the gluino decay chain. The use of short track segments reconstructed from the innermost tracking layers significantly improves the sensitivity to short chargino lifetimes. The results are found to be consistent with Standard Model predictions. Exclusion limits are set at 95% confidence level on the mass of charginos and gluinos for different chargino lifetimes. For a pure wino with a lifetime of about 0.2 ns, chargino masses up to 460 GeV are excluded. For the strong production channel, gluino masses up to 1.65 TeV are excluded assuming a chargino mass of 460 GeV and lifetime of 0.2 ns.

著者

原 和彦 金 信弘 大川 英希 佐藤 構二 受川 史彦 ATLAS Collaboration Hara K. Kim S.H. Okawa H. Sato K. Ukegawa F.

出版者

American Physical Society

雑誌

Physical Review D (ISSN:24700010)

巻号頁・発行日

vol.98, no.3, 2018-08-15

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Results from a search for supersymmetry in events with four or more charged leptons (electrons, muons and taus) are presented. The analysis uses a data sample corresponding to 36.1 fb(-1) of proton-proton collisions delivered by the Large Hadron Collider at root s = 13 TeV and recorded by the ATLAS detector. Four-lepton signal regions with up to two hadronically decaying taus are designed to target a range of supersymmetric scenarios that can be either enriched in or depleted of events involving the production and decay of a Z boson. Data yields are consistent with Standard Model expectations and results are used to set upper limits on the event yields from processes beyond the Standard Model. Exclusion limits are set at the 95% confidence level in simplified models of general gauge mediated supersymmetry, where Higgsino masses are excluded up to 295 GeV. In R-parity-violating simplified models with decays of the lightest supersymmetric particle to charged leptons, lower limits of 1.46, 1.06, and 2.25 TeV are placed on wino, slepton and gluino masses, respectively.

著者

原 和彦 佐藤 構二 受川 史彦 ATLAS Collaboration Kazuhiko HARA Koji SATO Fumihiko UKEGAWA

出版者

American Physical Society

雑誌

Physical review D (ISSN:24700010)

巻号頁・発行日

vol.101, no.1, 2020-01

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Combined measurements of Higgs boson production cross sections and branching fractions are presented. The combination is based on the analyses of the Higgs boson decay modes H→γγ, ZZ∗, WW∗, ττ, b¯b, μμ, searches for decays into invisible final states, and on measurements of off-shell Higgs boson production. Up to 79.8  fb−1 of proton–proton collision data collected at √s=13  TeV with the ATLAS detector are used. Results are presented for the gluon–gluon fusion and vector-boson fusion processes, and for associated production with vector bosons or top-quarks. The global signal strength is determined to be μ=1.11+0.09−0.08. The combined measurement yields an observed (expected) significance for the vector-boson fusion production process of 6.5σ (5.3σ). Measurements in kinematic regions defined within the simplified template cross section framework are also shown. The results are interpreted in terms of modifiers applied to the Standard Model couplings of the Higgs boson to other particles, and are used to set exclusion limits on parameters in two-Higgs-doublet models and in the simplified minimal supersymmetric Standard Model. No significant deviations from Standard Model predictions are observed.

著者

The ATLAS Collaboration Hara K. Kim S.H. Okawa H. Sato K. Ukegawa F.

出版者

Elsevier B.V.

雑誌

Physics letters. B (ISSN:03702693)

巻号頁・発行日

vol.765, pp.11-31, 2017-02

被引用文献数

23

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A search for dark matter pair production in association with a Higgs boson decaying to a pair of bottom quarks is presented, using 3.2 fb−1 of pp collisions at a centre-of-mass energy of 13 TeV collected by the ATLAS detector at the LHC. The decay of the Higgs boson is reconstructed as a high-momentum b¯b system with either a pair of small-radius jets, or a single large-radius jet with substructure. The observed data are found to be consistent with the expected backgrounds. Results are interpreted using a simplified model with a Z′Z′ gauge boson mediating the interaction between dark matter and the Standard Model as well as a two-Higgs-doublet model containing an additional Z′Z′ boson which decays to a Standard Model Higgs boson and a new pseudoscalar Higgs boson, the latter decaying into a pair of dark matter particles.