20 research outputs found

    ЭПИДЕМИОЛОГИЧЕСКИЙ НАДЗОР ЗА ХОЛЕРОЙ В РОССИИ В ПЕРИОД СЕДЬМОЙ ПАНДЕМИИ

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    In this work basic stages of formation of the epidemiological surveillance of cholera in Russia are described. In 1990-s for the first time zoning by epidemic manifestations of cholera was carried out at the level of subjects forming parts of Russia and other Republics of the Soviet Union with the introduction of differential tactics of epidemiological surveillance. Improvement of epidemiological surveillance of cholera was aimed at harmonization with the IHR (2005), integration of epidemiological surveillance of cholera and social-hygienic monitoring of water objects of I and II categories. Characterization of isolated Vibrio cholerae strains (1990−2014) on the genomic basis determined the emergence of new VNTR-genotypes of V. cholerae O1 ctxAB+ tcpA+, responsible for outbreaks, simultaneously with isolation of V. cholerae O1 ctxAB-tcpA- strains during monitoring of environmental objects for cholera. A viewpoint is considered of the beginning of the eighth cholera pandemic in the context of emergence of V. cholerae-torstrains with CTXφ prophage carrying ctxB gene of cholera toxin of classical biovar. Main directions of further enhancement of epidemiological surveillance include the study of basic data structures used in the epidemiological surveillance system, the use of zoning of municipal units of federal subjects with corresponding surveillance tactics and expected economic effect. Представлены основные этапы становления эпидемиологического надзора за холерой в России. В 1990-е гг. впервые проведено районирование на уровне субъектов, входящих в состав России и других республик Союза ,по типам эпидемических проявлений холеры с введением дифференцированной тактики эпидемиологического надзора. Совершенствование эпидемиологического надзора за холерой было направлено на гармонизацию с Международными медико-санитарными правилами (2005), интеграцию с социально-гигиеническим мониторингом водных объектов I и II категорий. При характеристике выделенных из объектов окружающей среды холерных вибрионов (1990−2014 гг.) Vibrio cholerae О1ctxAB-tcpA-на геномной основе установлено появление новых VNTR-генотипов V. cholerae О1 ctxAB+tcpA+, ответственных за вспышки высокоопасной инфекции. Высказана точка зрения о начале восьмой пандемии холеры, обусловленной V. cholerae О1 биовара el-tor с наличием в профаге CTXφ гена ctxB холерного токсина классического биовара. Основными направлениями совершенствования эпидемиологического надзора на современном этапе являются исследование структур основных данных, используемых для определения эпидпотенциала территорий; переход на районирование входящих в субъекты муниципальных образований с дифференцированной тактикой эпидемиологического надзора и ожидаемым экономическим эффектом. 

    Observation of quantum entanglement with top quarks at the ATLAS detector

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    Entanglement is a key feature of quantum mechanics with applications in fields such as metrology, cryptography, quantum information and quantum computation. It has been observed in a wide variety of systems and length scales, ranging from the microscopic to the macroscopic. However, entanglement remains largely unexplored at the highest accessible energy scales. Here we report the highest-energy observation of entanglement, in top–antitop quark events produced at the Large Hadron Collider, using a proton–proton collision dataset with a centre-of-mass energy of √s = 13 TeV and an integrated luminosity of 140 inverse femtobarns (fb)−1 recorded with the ATLAS experiment. Spin entanglement is detected from the measurement of a single observable D, inferred from the angle between the charged leptons in their parent top- and antitop-quark rest frames. The observable is measured in a narrow interval around the top–antitop quark production threshold, at which the entanglement detection is expected to be significant. It is reported in a fiducial phase space defined with stable particles to minimize the uncertainties that stem from the limitations of the Monte Carlo event generators and the parton shower model in modelling top-quark pair production. The entanglement marker is measured to be D = −0.537 ± 0.002 (stat.) ± 0.019 (syst.) for 340 GeV < mtt < 380 GeV. The observed result is more than five standard deviations from a scenario without entanglement and hence constitutes the first observation of entanglement in a pair of quarks and the highest-energy observation of entanglement so far

    Precise measurements of W- and Z-boson transverse momentum spectra with the ATLAS detector using pp collisions at t √s = 5.02 TeV and 13 TeV

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    Study of Z → llγ decays at √s = 8 TeV with the ATLAS detector

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    This paper presents a study of Z → llγ decays with the ATLAS detector at the Large Hadron Collider. The analysis uses a proton–proton data sample corresponding to an integrated luminosity of 20.2 fb−1 collected at a centre-ofmass energy √s = 8 TeV. Integrated fiducial cross-sections together with normalised differential fiducial cross-sections, sensitive to the kinematics of final-state QED radiation, are obtained. The results are found to be in agreement with stateof-the-art predictions for final-state QED radiation. First measurements of Z → llγ γ decays are also reported

    Search for leptoquark pair production decaying into te−te¯ + or tμ−t¯μ+ in multi-lepton final states in pp collisions at √s = 13 TeV with the ATLAS detector

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    A search for leptoquark pair production decaying into te−te¯ + or tμ−t¯μ+ in final states with multiple leptons is presented. The search is based on a dataset of pp collisions at √s = 13 TeV recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb−1. Four signal regions, with the requirement of at least three light leptons (electron or muon) and at least two jets out of which at least one jet is identified as coming from a b-hadron, are considered based on the number of leptons of a given flavour. The main background processes are estimated using dedicated control regions in a simultaneous fit with the signal regions to data. No excess above the Standard Model background prediction is observed and 95% confidence level limits on the production cross section times branching ratio are derived as a function of the leptoquark mass. Under the assumption of exclusive decays into te− (tμ−), the corresponding lower limit on the scalar mixed-generation leptoquark mass mLQd mix is at 1.58 (1.59) TeV and on the vector leptoquark mass mU˜1 at 1.67 (1.67) TeV in the minimal coupling scenario and at 1.95 (1.95) TeV in the Yang–Mills scenario

    Measurements of the production cross-section for a Z boson in association with b- or c-jets in proton–proton collisions at √s = 13 TeV with the ATLAS detector

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    This paper presents a measurement of the production cross-section of a Z boson in association with bor c-jets, in proton–proton collisions at √s = 13 TeV with the ATLAS experiment at the Large Hadron Collider using data corresponding to an integrated luminosity of 140 fb−1. Inclusive and differential cross-sections are measured for events containing a Z boson decaying into electrons or muons and produced in association with at least one b-jet, at least one c-jet, or at least two b-jets with transverse momentum pT > 20 GeV and rapidity |y| < 2.5. Predictions from several Monte Carlo generators based on next-to-leading-order matrix elements interfaced with a parton-shower simulation, with different choices of flavour schemes for initial-state partons, are compared with the measured cross-sections. The results are also compared with novel predictions, based on infrared and collinear safe jet flavour dressing algorithms. Selected Z+ ≥ 1 c-jet observables, optimized for sensitivity to intrinsic-charm, are compared with benchmark models with different intrinsic-charm fractions

    Search for resonances decaying into photon pairs in 139 fb−1 of pp collisions at √s = 13 TeV with the ATLAS detector

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    Searches for new resonances in the diphoton final state, with spin 0 as predicted by theories with an extended Higgs sector and with spin 2 using a warped extra-dimension benchmark model, are presented using 139 fb−1 of √s = 13 TeV pp collision data collected by the ATLAS experiment at the LHC. No significant deviation from the Standard Model is observed and upper limits are placed on the production cross-section times branching ratio to two photons as a function of the resonance mass

    Constraints on spin-0 dark matter mediators and invisible Higgs decays using ATLAS 13 TeV pp collision data with two top quarks and missing transverse momentum in the final state

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    This paper presents a statistical combination of searches targeting final states with two top quarks and invisible particles, characterised by the presence of zero, one or two leptons, at least one jet originating from a b-quark and missing transverse momentum. The analyses are searches for phenomena beyond the Standard Model consistent with the direct production of dark matter in pp collisions at the LHC, using 139 fb−1 of data collected with the ATLAS detector at a centre-of-mass energy of 13 TeV. The results are interpreted in terms of simplified dark matter models with a spin-0 scalar or pseudoscalar mediator particle. In addition, the results are interpreted in terms of upper limits on the Higgs boson invisible branching ratio, where the Higgs boson is produced according to the Standard Model in association with a pair of top quarks. For scalar (pseudoscalar) dark matter models, with all couplings set to unity, the statistical combination extends the mass range excluded by the best of the individual channels by 50 (25) GeV, excluding mediator masses up to 370 GeV. In addition, the statistical combination improves the expected coupling exclusion reach by 14% (24%), assuming a scalar (pseudoscalar) mediator mass of 10 GeV. An upper limit on the Higgs boson invisible branching ratio of 0.38 (0.30+0.13−0.09) is observed (expected) at 95% confidence level

    Software performance of the ATLAS track reconstruction for LHC run 3

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    Charged particle reconstruction in the presence of many simultaneous proton–proton (pp) collisions in the LHC is a challenging task for the ATLAS experiment’s reconstruction software due to the combinatorial complexity. This paper describes the major changes made to adapt the software to reconstruct high-activity collisions with an average of 50 or more simultaneous pp interactions per bunch crossing (pileup) promptly using the available computing resources. The performance of the key components of the track reconstruction chain and its dependence on pile-up are evaluated, and the improvement achieved compared to the previous software version is quantified. For events with an average of 60 pp collisions per bunch crossing, the updated track reconstruction is twice as fast as the previous version, without significant reduction in reconstruction efficiency and while reducing the rate of combinatorial fake tracks by more than a factor two

    Constraints on simplified dark matter models involving an s-channel mediator with the ATLAS detector in pp collisions at s = 13 TeV

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