The ATLAS data quality defect database system Golling, T.; Hayward, H. S.; Onyisi, P. U. E. ...
European physical journal. C, Particles and fields,
04/2012, Letnik:
72, Številka:
4
Journal Article
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The ATLAS experiment at the Large Hadron Collider has implemented a new system for recording information on detector status and data quality, and for transmitting this information to users performing ...physics analysis. This system revolves around the concept of “defects,” which are well-defined, fine-grained, unambiguous occurrences affecting the quality of recorded data. The motivation, implementation, and operation of this system is described.
Searches are performed for nonresonant and resonant di-Higgs boson production in the b¯bγγ final state. The dataset used corresponds to an integrated luminosity of 139 fb−1 of proton–proton ...collisions at a center-of-mass energy of 13 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. No excess above the expected background is found and upper limits on the di-Higgs boson production cross sections are set. A 95% confidence-level upper limit of 4.2 times the cross section predicted by the Standard Model is set on pp→HH nonresonant production, where the expected limit is 5.7 times the Standard Model predicted value. The expected constraints are obtained for a background hypothesis excluding pp→HH production. The observed (expected) constraints on the Higgs boson trilinear coupling modifier κλ are determined to be −1.5,6.7 (−2.4,7.7) at 95% confidence level, where the expected constraints on κλ are obtained excluding pp→HH production from the background hypothesis. For resonant production of a new hypothetical scalar particle X (X→HH→b¯bγγ), limits on the cross section for pp→X→HH are presented in the narrow-width approximation as a function of mX in the range 251 GeV≤mX≤1000 GeV. The observed (expected) limits on the cross section for pp→X→HH range from 640 fb to 44 fb (391 fb to 46 fb) over the considered mass range.
A search for heavy resonances decaying into a W or Z boson and a Higgs boson produced in proton − proton collisions at the Large Hadron Collider at √s = 13 TeV is presented. The analysis utilizes the ...dominant W → q¯q′ or Z → q¯q and H → b¯b decays with substructure techniques applied to large-radius jets. A sample corresponding to an integrated luminosity of 139 fb−1 collected with the ATLAS detector is analyzed and no significant excess of data is observed over the background prediction. The results are interpreted in the context of the heavy vector triplet model with spin-1 W′ and Z′ bosons. Upper limits on the cross section are set for resonances with mass between 1.5 and 5.0 TeV, ranging from 6.8 to 0.53 fb for W → WH and from 8.7 to 0.53 fb for Z′ → ZH at the 95% confidence level.
A combination of fifteen top quark mass measurements performed by the ATLAS and CMS experiments at the LHC is presented. The datasets used correspond to an integrated luminosity of up to 5 and 20 ...fb-1 of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, respectively. The combination includes measurements in top quark pair events that exploit both the semileptonic and hadronic decays of the top quark, and a measurement using events enriched in single top quark production via the electroweak t channel. The combination accounts for the correlations between measurements and achieves an improvement in the total uncertainty of 31% relative to the most precise input measurement. The result is mt = 172.52 ± 0.14(stat) ± 0.30(syst) GeV, with a total uncertainty of 0.33 GeV.
ATLAS measured the centrality dependence of the dijet yield using 165 nb-1 of p + Pb data collected at $\sqrt{^SNN}$ =8.16 TeV in 2016. The event centrality, which reflects the p+Pb impact parameter, ...is characterized by the total transverse energy registered in the Pb-going side of the forward calorimeter. The central-to-peripheral ratio of the scaled dijet yields, RCP, is evaluated, and the results are presented as a function of variables that reflect the kinematics of the initial hard parton scattering process. The RCP shows a scaling with the Bjorken x of the parton originating from the proton, xp, while no such trend is observed as a function of xPb. This analysis provides unique input to understanding the role of small proton spatial configurations in p + Pb collisions by covering parton momentum fractions from the valence region down to xp ~ 10-3 and xPb ~ 4 × 10-4.
A measurement of the mass of the Higgs boson combining the H → ZZ* → 4ℓ and H → γγ decay channels is presented. The result is based on 140 fb–1 of proton-proton collision data collected by the ATLAS ...detector during LHC run 2 at a centre-of-mass energy of 13 TeV combined with the run 1 ATLAS mass measurement, yielding a Higgs boson mass of 125.11 ± 0.09 (stat.) ± 0.06 (syst.) = 125.11 ± 0.11 GeV. This corresponds to a 0.09 % precision achieved on this fundamental parameter of the Standard Model of particle physics.
A search for quantum black holes in electron+jet and muon+jet invariant mass spectra is performed with 140 fb −1 of data collected by the ATLAS detector in proton-proton collisions at √s=13 TeV at ...the Large Hadron Collider. The observed invariant mass spectrum of lepton+jet pairs is consistent with Standard Model expectations. Upper limits are set at 95% confidence level on the production cross section times branching fractions for quantum black holes decaying into a lepton and a quark in a search region with invariant mass above 2.0 TeV. The resulting quantum black hole lower mass threshold limit is 9.2 TeV in the Arkani-Hamed-Dimopoulos-Dvali model, and 6.8 TeV in the Randall-Sundrum model.
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