30 research outputs found

    Differential cross-section measurements of the production of four charged leptons in association with two jets using the ATLAS detector

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    Differential cross-sections are measured for the production of four charged leptons in association with two jets. These measurements are sensitive to final states in which the jets are produced via the strong interaction as well as to the purely-electroweak vector boson scattering process. The analysis is performed using proton-proton collision data collected by ATLAS at √s = 13 TeV and with an integrated luminosity of 140 fb−1. The data are corrected for the effects of detector inefficiency and resolution and are compared to state-of-the-art Monte Carlo event generator predictions. The differential cross-sections are used to search for anomalous weak-boson self-interactions that are induced by dimension-six and dimension-eight operators in Standard Model effective field theory

    Revisitando a técnica de eletroconvulsoterapia no contexto da reforma psiquiátrica brasileira

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    A técnica de eletroconvulsoterapia é uma modalidade interventiva da psiquiatria, inaugurada na década de 30 e utilizada ininterruptamente até hoje. A discussão que envolve essa técnica é bastante polêmica, e não porta uma reflexão dialógica entre os campos de saberes afins a ela. Foi proposta do presente estudo realizar uma leitura teórica da técnica, a partir do conjunto teórico-prático do campo da saúde mental, tendo como referência as orientações éticas do Movimento de Reforma Psiquiátrica, intencionando discutir a sua coerência para as práticas de cuidado nesse campo. Problematizar e recomplexificar o tema foi o objetivo geral deste artigo, alcançado através de uma revisão bibliográfica do assunto. Foram identificadas pontes entre a proposta da técnica de ECT e as concepções que embasaram a assistência manicomial/hospitalocêntrica, e, por isso, questionamos a sua coerência para o campo interventivo contemporâneo da saúde mental, que se propõe a dar seguimento às desconstruções do paradigma clássico da psiquiatria

    Search for Higgs boson decays into a pair of pseudoscalar particles in the final state with the ATLAS detector in collisions at

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    This paper presents a search for decays of the Higgs boson with a mass of 125 GeV into a pair of new pseudoscalar particles, H -> aa, where one a-boson decays into a b-quark pair and the other into a muon pair. The search uses 139 fb(-1) of proton-proton collision data at a center-of-mass energy root s = 13 TeV recorded between 2015 and 2018 by the ATLAS experiment at the LHC. A narrow dimuon resonance is searched for in the invariant mass spectrum between 16 GeV and 62 GeV. The largest excess of events above the Standard Model backgrounds is observed at a dimuon invariant mass of 52 GeV and corresponds to a local (global) significance of 3.3 sigma (1.7 sigma). Upper limits at 95% confidence level are placed on the branching ratio of the Higgs boson to the bb mu mu final state, beta(H -> aa -> bb mu mu), and are in the range 0.2-4.0 x 10(-4), depending on the signal mass hypothesis

    Search for events with a pair of displaced vertices from long-lived neutral particles decaying into hadronic jets in the ATLAS muon spectrometer in collisions at

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    A search for events with two displaced vertices from long-lived particle (LLP) pairs using data collected by the ATLAS detector at the LHC is presented. This analysis uses 139 fb(-1) of proton-proton collision data at root s=13 TeV recorded in 2015-2018. The search employs techniques for reconstructing vertices of LLPs decaying to jets in the muon spectrometer displaced between 3 and 14 m with respect to the primary interaction vertex. The observed numbers of events are consistent with the expected background and limits for several benchmark signals are determined. For the Higgs boson with a mass of 125 GeV, the paper reports the first exclusion limits for branching fractions into neutral long-lived particles below 0.1%, while branching fractions above 10% are excluded at 95% confidence level for LLP proper lifetimes ranging from 4 cm to 72.4 m. In addition, the paper present the first results for the decay of LLPs into (tt) over bar in the ATLAS muon spectrometer

    Measurements of jet observables sensitive to -quark fragmentation in events at the LHC with the ATLAS detector

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    Several observables sensitive to the fragmentation of b quarks into b hadrons are measured using 36 fb(-1) of root s = 13 TeV proton-proton collision data collected with the ATLAS detector at the LHC. Jets containing b hadrons are obtained from a sample of dileptonic (tt) over bar events, and the associated set of charged-particle tracks is separated into those from the primary pp interaction vertex and those from the displaced b-decay secondary vertex. This division is used to construct observables that characterize the longitudinal and transverse momentum distributions of the b hadron within the jet. The measurements have been corrected for detector effects and provide a test of heavy-quark-fragmentation modeling at the LHC in a system where the top-quark decay products are color connected to the proton beam remnants. The unfolded distributions are compared with the predictions of several modern Monte Carlo parton-shower generators and generator tunes, and a wide range of agreement with the data is observed, with p values varying from 5 x 10(-4) to 0.98. These measurements complement similar measurements from e(+)e(-) collider experiments in which the b quarks originate from a color singlet Z/gamma*

    Constraints on Higgs boson production with large transverse momentum using decays in the ATLAS detector

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    This paper reports constraints on Higgs boson production with transverse momentum above 1 TeV. The analyzed data from proton-proton collisions at a center-of-mass energy of 13 TeV were recorded with the ATLAS detector at the Large Hadron Collider from 2015 to 2018 and correspond to an integrated luminosity of 136 fb(-1.) Higgs bosons decaying into b (b) over bar are reconstructed as single large-radius jets recoiling against a hadronic system and are identified by the experimental signature of two b-hadron decays. The experimental techniques are validated in the same kinematic regime using the Z -> b (b) over bar process. The 95% confidence-level upper limit on the cross section for Higgs boson production with transverse momentum above 450 GeV is 115 fb, and above 1 TeV it is 9.6 fb. The Standard Model cross section predictions for a Higgs boson with a mass of 125 GeV in the same kinematic regions are 18.4 fb and 0.13 fb, respectively
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