2,880 research outputs found

    Correlation between surface tension, work of adhesion in liquid metals/ceramic systems, and acoustic parameters

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    In the paper, a correlation between acoustic velocities V, elastic moduli M, and densities ρ, with surface tension σm, and work of adhesion Wad of different liquid metals on a given ceramic is studied and demonstrated. Simulation program is developed and used for scanning acoustic microscopy (SAM) under operating conditions, which favour the generation of acoustic waves. As found, for the given systems, all investigated acoustic parameters exhibit good dependences with both σm and Wad. Analysis and quantification of the results lead to the determination of semi-empirical formulas.В статті вперше демонструється кореляція між акустичними швидкостями V, пружніми модулями M, густинами ρ та поверхневим натягом σm, а також роботою адгезії Wad різних рідких металів на фіксованій кераміці. Використовується обчислювальна програма для сканувального акустичного мікроскопу (САМ) за умов, що є сприятливими задля ґенерування акустичних хвиль. Виявлено, що для конкретних систем усі досліджені акустичні параметри демонструють хорошу залежність від поверхневого натягу та роботи адгезії. Аналіза та кількісне визначення результатів привели до встановлення напівемпіричних формул.В статье исследуется и впервые демонстрируется корреляция между акустическими скоростями V, упругими модулями M, плотностями ρ и поверхностным натяжением σm, а также работой адгезии Wad различных жидких металлов на фиксированной керамике. Используется вычислительная программа для сканирующего акустического микроскопа (САМ) в условиях, благоприятных для генерирования акустических волн. Обнаружено, что для конкретных систем все исследованные акустические параметры демонстрируют хорошую зависимость от поверхностного натяжения и работы адгезии. Анализ и количественное определение результатов привели к установлению полуэмпирических формул

    Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

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    This paper presents measurements of the W+μ+νW^+ \rightarrow \mu^+\nu and WμνW^- \rightarrow \mu^-\nu cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

    Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector

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    A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13  TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139  fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV

    Search for direct stau production in events with two hadronic tau-leptons in root s=13 TeV pp collisions with the ATLAS detector

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    A search for the direct production of the supersymmetric partners ofτ-leptons (staus) in final stateswith two hadronically decayingτ-leptons is presented. The analysis uses a dataset of pp collisions corresponding to an integrated luminosity of139fb−1, recorded with the ATLAS detector at the LargeHadron Collider at a center-of-mass energy of 13 TeV. No significant deviation from the expected StandardModel background is observed. Limits are derived in scenarios of direct production of stau pairs with eachstau decaying into the stable lightest neutralino and oneτ-lepton in simplified models where the two staumass eigenstates are degenerate. Stau masses from 120 GeV to 390 GeV are excluded at 95% confidencelevel for a massless lightest neutralino

    Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector

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    Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente

    Aspect immuno-pathologique de la maladie hémolytique du nouveau-né liée à une incompatibilité RH1

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    La maladie hémolytique du nouveau né liée à une incompatibilité Rh1 est l’exemple d’allo-immunisation foeto-maternelle anti-érythrocytaire. Les anticorps générés peuvent provoquer par divers mécanismes immunologiques (opsonisation, cytotoxicité anticorps dépendante,..) la lyse des hématies fœtales. Cette hémolyse entraine l’anémie parfois sévère mais surtout la neurotoxicité fœtale causée par les produits de  dégradation de l’hémoglobine. Elle peut aboutir à la mort fœtale  ou à des retards mentaux importants. Le dépistage de cette affection, par des tests immuni-hématologiques simples (groupge étythrocytaire, RAI) est indispensable et fait partie du bilan biologique de surveillance de toute grossesse. Sa prévention par l’administration d’immunoglobulines, n’est malheureusement  pas toujours de mise comme l’atteste cette observation d’issue fatale

    Search for W\u27→tb decays in the hadronic final state using ppcollisions at √s=13TeVwith the ATLAS detector

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    A search for W\u27-boson production in the W\u27→t¯b→q¯q\u27b¯b decay channel is presented using 36.1fb−1of 13TeV proton–proton collision data collected by the ATLAS detector at the Large Hadron Collider in 2015 and 2016. The search is interpreted in terms of both a left-handed and a right-handed chiral W\u27 boson within the mass range 1–5 TeV. Identification of the hadronically decaying top quark is performed using jet substructure tagging techniques based on a shower deconstruction algorithm. No significant deviation from the Standard Model prediction is observed and the results are expressed as upper limits on the W\u27→t¯bproduction cross-section times branching ratio as a function of the W\u27-boson mass. These limits exclude W\u27 bosons with right-handed couplings with masses below 3.0TeV and W\u27 bosons with left-handed couplings with masses below 2.9TeV, at the 95% confidence level

    Measurement of jet fragmentation in Pb+Pb and pp collisions at √s NN =5.02 TeV with the ATLAS detector

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    This paper presents a measurement of jet fragmentation functions in 0.49 nb −1 of Pb+Pb collisions and 25 pb −1 of pp collisions at √ sNN =5.02 TeV collected in 2015 with the ATLAS detector at the LHC. These measurements provide insight into the jet quenching process in the quark-gluon plasma created in the aftermath of ultra-relativistic collisions between two nuclei. The modifications to the jet fragmentation functions are quantified by dividing the measurements in Pb+Pb collisions by baseline measurements in pp collisions. This ratio is studied as a function of the transverse momentum of the jet, the jet rapidity, and the centrality of the collision. In both collision systems, the jet fragmentation functions are measured for jets with transverse momentum between 126 GeV and 398 GeV and with an absolute value of jet rapidity less than 2.1. An enhancement of particles carrying a small fraction of the jet momentum is observed, which increases with centrality and with increasing jet transverse momentum. Yields of particles carrying a very large fraction of the jet momentum are also observed to be enhanced. Between these two enhancements of the fragmentation functions a suppression of particles carrying an intermediate fraction of the jet momentum is observed in Pb+Pb collisions. A small dependence of the modifications on jet rapidity is observed

    Top-quark mass measurement in the all-hadronic tt¯ decay channel at √s=8 TeV with the ATLAS detector

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    The top-quark mass is measured in the all-hadronic top-antitop quark decay channel using proton-proton collisions at a centre-of-mass energy of √s=8 TeV with the ATLAS detector at the CERN Large Hadron Collider. The data set used in the analysis corresponds to an integrated luminosity of 20.2 fb−1. The large multi-jet background is modelled using a data-driven method. The top-quark mass is obtained from template fits to the ratio of the three-jet to the dijet mass. The three-jet mass is obtained from the three jets assigned to the top quark decay. From these three jets the dijet mass is obtained using the two jets assigned to the W boson decay. The top-quark mass is measured to be 173.72 ± 0.55 (stat.) ± 1.01 (syst.) GeV

    Search for lepton-flavour-violating decays of the Higgs and Z bosons with the ATLAS detector