16 research outputs found

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

    Get PDF
    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

    Software performance of the ATLAS track reconstruction for LHC run 3

    Get PDF
    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 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

    Get PDF
    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

    Search for heavy Majorana or Dirac neutrinos and right-handed W gauge bosons in final states with charged leptons and jets in pp collisions at √s = 13 TeV with the ATLAS detector

    Get PDF
    A search for heavy right-handed Majorana or Dirac neutrinos NR and heavy right-handed gauge bosons WR is performed in events with energetic electrons or muons, with the same or opposite electric charge, and energetic jets. The search is carried out separately for topologies of clearly separated final-state products (“resolved” channel) and topologies with boosted final states with hadronic and/or leptonic products partially overlapping and reconstructed as a large-radius jet (“boosted” channel). The events are selected from pp collision data at the LHC with an integrated luminosity of 139 fb−1 collected by the ATLAS detector at √s = 13 TeV. No significant deviations from the Standard Model predictions are observed. The results are interpreted within the theoretical framework of a left-right symmetric model, and lower limits are set on masses in the heavy righthanded WR boson and NR plane. The excluded region extends to about m(WR) = 6.4 TeV for both Majorana and Dirac NR neutrinos at m(NR) < 1 TeV. NR with masses of less than 3.5 (3.6) TeV are excluded in the electron (muon) channel at m(WR) = 4.8 TeV for the Majorana neutrinos, and limits of m(NR) up to 3.6 TeV for m(WR) = 5.2 (5.0) TeV in the electron (muon) channel are set for the Dirac neutrinos. These constitute the most stringent exclusion limits to date for the model considered

    Deep generative models for fast photon shower simulation in ATLAS

    Get PDF
    The need for large-scale production of highly accurate simulated event samples for the extensive physics programme of the ATLAS experiment at the Large Hadron Collider motivates the development of new simulation techniques. Building on the recent success of deep learning algorithms, variational autoencoders and generative adversarial networks are investigated for modelling the response of the central region of the ATLAS electromagnetic calorimeter to photons of various energies. The properties of synthesised showers are compared with showers from a full detector simulation using geant4. Both variational autoencoders and generative adversarial networks are capable of quickly simulating electromagnetic showers with correct total energies and stochasticity, though the modelling of some shower shape distributions requires more refinement. This feasibility study demonstrates the potential of using such algorithms for ATLAS fast calorimeter simulation in the future and shows a possible way to complement current simulation techniques

    Search for doubly charged Higgs boson production in multi-lepton final states using 139 fb−1 of proton–proton collisions at s√ = 13 TeV with the ATLAS detector

    Get PDF
    A search for pair production of doubly charged Higgs bosons (H±± ), each decaying into a pair of prompt, isolated, and highly energetic leptons with the same electric charge, is presented. The search uses a proton–proton collision data sample at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 139 fb−1 recorded by the ATLAS detector during Run 2 of the Large Hadron Collider (LHC). This analysis focuses on same-charge leptonic decays, H±±→ℓ±ℓ′± where ℓ,ℓ′=e,μ,τ, in two-, three-, and four-lepton channels, but only considers final states which include electrons or muons. No evidence of a signal is observed. Corresponding upper limits on the production cross-section of a doubly charged Higgs boson are derived, as a function of its mass m(H±±), at 95% confidence level. Assuming that the branching ratios to each of the possible leptonic final states are equal, B(H±±→e±e±)=B(H±±→e±μ±)=B(H±±→μ±μ±)=B(H±±→e±τ±)=B(H±±→μ±τ±)=B(H±±→τ±τ±)=1/6, the observed (expected) lower limit on the mass of a doubly charged Higgs boson is 1080 GeV (1065 GeV) within the left-right symmetric type-II seesaw model, which is the strongest limit to date produced by the ATLAS Collaboration. Additionally, this paper provides the first direct test of the Zee–Babu neutrino mass model at the LHC, yielding an observed (expected) lower limit of m(H±±) = 900 GeV (880 GeV)

    Observation of four-top-quark production in the multilepton final state with the ATLAS detector

    Get PDF
    This paper presents the observation of four-top-quark (tt¯tt¯) production in proton-proton collisions at the LHC. The analysis is performed using an integrated luminosity of 140 fb−1 at a centre-of-mass energy of 13 TeV collected using the ATLAS detector. Events containing two leptons with the same electric charge or at least three leptons (electrons or muons) are selected. Event kinematics are used to separate signal from background through a multivariate discriminant, and dedicated control regions are used to constrain the dominant backgrounds. The observed (expected) significance of the measured tt¯tt¯ signal with respect to the standard model (SM) background-only hypothesis is 6.1 (4.3) standard deviations. The tt¯tt¯ production cross section is measured to be 22.5+6.6−5.5 fb, consistent with the SM prediction of 12.0±2.4 fb within 1.8 standard deviations. Data are also used to set limits on the three-top-quark production cross section, being an irreducible background not measured previously, and to constrain the top-Higgs Yukawa coupling and effective field theory operator coefficients that affect tt¯tt¯ production

    Resposta hematológica do cascudo ornamental amazônico Peckoltia oligospila ao estresse de transporte

    No full text
    RESUMO O objetivo deste trabalho foi avaliar as respostas hematológicas do acari-bola Peckoltia oligospila submetido ao estresse de transporte. Variações nos parâmetros de sangue foram analisadas às zero, seis, 24, 48, 72 e 96 horas após o transporte. Respostas ao estresse foram observadas entre zero e seis horas do transporte, mas a maioria dos parâmetros retornou aos valores basais em 24 horas. O tempo de zero hora (momento imediato após transporte) foi o mais crítico, com valores elevados de glicemia, eritrócitos e eritroblastos. Respostas secundárias tardias foram observadas para a proteína plasmática total, o volume corpuscular médio (VCM) e a hemoglobina corpuscular média (HCM) em seis horas após o transporte dos peixes, retornando aos valores basais após esse período. O número de leucócitos não sofreu alterações após o transporte. O estresse de transporte não comprometeu a fisiologia de P. oligospila, o que indica que esse peixe é resistente ao estresse se comparado com outras espécies. Porém, recomenda-se que não se realize qualquer outro procedimento estressante durante pelo menos 24 horas da recuperação dos peixes após transporte, para garantir a saúde e a sobrevivência dos animais transportados

    Attalea speciosa mesocarp flour in-depth characterization and its application for the development of new bakery products

    No full text
    Non-conventional food plants (NFPs) present themselves as a viable and efficient alternative for replacing the food products we consume today. Presenting a huge nutritional, chemical, physical, and biological potential, these plants are usually abundant and not competitors with other vegetable matrices used for human consumption.1 Attalea speciosa (Mart. Ex Spreng - Babassu) is a palm tree from the botanical family Arecaceae found in Brazil, and its mesocarp (BM) represents about 20.4% of the fruit and most of its application it’s in the manufacture of animal feed.2 Thus, the present work aimed to deepen the study the nutritional characterization of BM by AOAC methods; the determination, by chromatographic methods, of free sugars (HPLC-RI), fatty acids (GC-FID), and organic acids content (UPLC-DAD); and the study of the phenolic profile (HPLC-DAD/ESI(MS) and bioactivities (antioxidant, antimicrobial, anti-inflammatory and cytotoxicity activities) of the hydroethanolic extracts. Furthermore, given the possible industrial application, bakery products (bread) were developed with 12, 18, and 24% substitutions of wheat flour by BM flour. BM flour presented low moisture, fat, ash levels, being carbohydrates the main macronutrients, and palmitic (C16:0) and stearic (C18:0) acids were the main fatty acids found in the sample. Regarding phenolic composition, nine phenolic compounds were tentatively identified, six flavan-3-ols (catechin and epicatechin derivatives) and three Oglycosylated flavonoids (quercetin derivatives). Specifically, the flavan-3-ols group represented 99% of total amount of phenolic compounds mainly due to the presence of β-type (Epi)catechin dimer. The hydroethanolic extract of BM showed a high antioxidant capacity to inhibit lipid peroxidation and high anti-hemolytic capacity, showing an IC50 99% and 75% more effective than the positive control used (Trolox) in these assays, respectively. Moreover, it was able to inhibit all the tumor cell lines tested (MCF-7, NCIH460, CaCo, and AGS), however, it showed some toxicity towards healthy cells of PLP2 and VERO lines. The results obtained for the antibacterial activity of the BM extract were lower when compared to the positive controls used (E211 and E224). Comparing the results obtained with 100% wheat flour products, it was noted that the formulations with substitutions by BM presented remarkable results, providing a reasonable increase in the PUFAs content (despite decreasing protein content), maintaining the antioxidant capacity with lower IC50 values than the positive control used, and not presenting hepatotoxic activity (first validation of this flour for the incorporation in food matrices). In general, the formulation B24 was the one that presented greater similarity to the control bread (B0), relatively to the nutritional aspects, however, concerning the physical parameters it was the one that presented bigger discrepancy, especially regarding the specific volume, texture, and the color parameter L* (luminosity), tending for a darker and opaque coloration. All the formulations presented higher percentages of loss of rheological characteristics in the first three days of elaboration, however, formulation B24 was the one that presented the lowest percentage. This study presented innovative results regarding the nutritional, chemical and bioactive characterization of both the babassu mesocarp itself and the bread made from it, showing great potential to be applied in the food industry, however, there is still much to explore, especially in preparations that do not yet use non-conventional ingredients.The authors thanks to the Fundação para a Ciência e Tecnologia (FCT; Portugal) for financial support through national funds FCT/MCTES to CIMO (UIDB/00690/2020), the national funding for F.C.T. and P.I. and through the institutional scientific employment program contract for C.P., M.I.D, and L.B. To ERDF through the Regional Operational Program North 2020 within the scope of the project GreenHealth-Norte-01-0145-FEDER-000042. To Serbian Ministry of Education, Science and Technological Development (Contract No. 451-03-9/2021-14/200007).info:eu-repo/semantics/publishedVersio

    Caracterización detallada de la harina del mesocarpio de Attalea speciosa y su aplicación para el desarrollo de nuevos productos de panadería

    No full text
    Las plantas alimenticias no convencionales se presentan como una alternativa viable y eficiente para reemplazar los productos alimenticios que consumimos hoy. Presentando un enorme potencial nutricional, químico, físico y biológico, estas plantas suelen ser abundantes y no competidoras de otras matrices vegetales [1]. Attalea speciosa (Mart. Ex Spreng - Babassu) es una palmera que se encuentra en Brasil, y su mesocarpio (MB) representa cerca del 20,4% del fruto, presentando aplicabilidad en la fabricación de alimentos para animales [2]. Así, el presente trabajo tuvo como objetivo profundizar el estudio de la caracterización nutricional de MB por métodos de la AOAC; la determinación del contenido de azúcares libres (HPLC-RI), ácidos grasos (GC-FID), ácidos orgánicos (UPLC-DAD) y compuestos fenólicos (HPLCDAD/ ESI(MS); y propiedades bioactivas (antioxidante, antimicrobiana, antiinflamatoria, citotóxica y nefrotoxicidad) de los extractos hidroetanólicos. Además, se desarrollaron productos de panadería (pan) con 12, 18 y 24% de sustitución de harina de trigo por harina MB. La harina presentó bajos niveles de humedad, grasa y cenizas, siendo los carbohidratos los principales macronutrientes, y los ácidos palmítico y esteárico los principales ácidos grasos. Se identificó tentativamente nueve compuestos fenólicos, seis flavan-3-oles (99% de la cantidad total, sobre todo por la presencia del dímero de (epi)catequina tipo β) y tres flavonoides O-glicosilados. El extracto hidroetanólico mostró una alta capacidad antioxidante y antihemolítica, mostrando una IC50 de 99% y 75% más efectiva que el control positivo (Trolox), respectivamente. Además, fue capaz de inhibir todas las líneas celulares tumorales, per mostró cierta toxicidad hacia las células sanas. Para la actividad antibacteriana fueron obtenidas concentraciones mínimas inhibitorias inferiores a la de los controles positivos (E211 y E224). Finalmente, se observó que las formulaciones de pan con sustituciones presentaron un aumento razonable en el contenido de PUFAs, manteniendo la capacidad antioxidante con valores de IC50 más bajos que los del control positivo, y no presentando actividad hepatotóxica (primera validación de esta harina para la incorporación en matrices alimentarias). En general, la formulación B24 fue la que presentó mayor similitud con el pan control, en relación a los aspectos nutricionales, sin embargo, en cuanto a los parámetros físicos fue la que presentó mayor discrepancia (en volumen específico, textura, y luminosidad). Todas las formulaciones presentaron mayores porcentajes de pérdida de características reológicas en los primeros tres días de elaboración. Este estudio presentó resultados innovadores en cuanto a la caracterización nutricional, química y bioactiva tanto del propio mesocarpio de babasú como del pan elaborado a partir de él, mostrando un gran potencial para ser aplicado en la industria alimentaria, sin embargo, aún queda mucho por explorar, especialmente en preparaciones que todavía no use ingredientes no convencionalesA Fundação para a Ciência e Tecnologia (FCT; Portugal) por el apoyo financiero FCT/MCTES a CIMO CIMO (UIDB/00690/2020 e UIDP/00690/2020), SusTEC (LA/P/0007/2020) y beca de doctorado A. Saldanha (2021.08346.BD); la financiación nacional para F.C.T. y P. I. y a través del contrato del programa de empleo científico institucional para C.P., M.I.D y L.B. A FEDER a través del Programa Operativo Regional Norte 2020 (GreenHealth-Norte-01-0145-FEDER-000042. Al Ministerio de Educación, Ciencia y Desarrollo Tecnológico de Serbia (Contrato No. 451-03-9/2021-14/200007).info:eu-repo/semantics/publishedVersio
    corecore