30 research outputs found

    Influence of the type of rare-earth cation on electrical properties of Ba(Zr,Ti)O3 ceramics

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    En este artículo es investigado el efecto del radio iónico de diferentes cationes de tierras raras sobre las propiedades eléctricas del compuesto Ba(Zr,Ti)O3. La cerámica BaZr0.09Ti0.9O3 fue dopada con iones de Gd3+, Pr3+ y La3+, sustituyendo un 5 % de contenido de cationes Ba2+. Los resultados muestran que el coeficiente de difusividad se incrementa con el aumento del radio iónico, mientras el carácter de la transición de fase permanece casi constante, de acuerdo con el modelo fenomenológico de Santos-Eiras. En todas las muestras se reporta un comportamiento no relajador. El proceso de conductividad iónica en el BaZr0.09Ti0.9O3 aparece a 200 ºC, valor inferior al observado en el material cerámico BaTiO3. El valor de energía de activación en el proceso de conductividad del BaZr0.09Ti0.9O3 (Ea= 0.81 eV) indica un mecanismo de compensación de carga en la estructura cristalina similar al BaTiO3, es decir vacancias de oxígeno simplemente ionizadas. Para el compuesto BaZr0.09Ti0.9O3 dopado con iones Gd3+, Pr3+ y La3+ aparece además un mecanismo de conducción de electrones, debido a la sustitución del Ba2+.Postprint (published version

    Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

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    A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

    Measurement of the W boson polarisation in ttˉt\bar{t} events from pp collisions at s\sqrt{s} = 8 TeV in the lepton + jets channel with ATLAS

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    Measurements of top-quark pair differential cross-sections in the eμe\mu channel in pppp collisions at s=13\sqrt{s} = 13 TeV using the ATLAS detector

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    Search for dark matter in association with a Higgs boson decaying to bb-quarks in pppp collisions at s=13\sqrt s=13 TeV with the ATLAS detector

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    Measurement of the bbb\overline{b} dijet cross section in pp collisions at s=7\sqrt{s} = 7 TeV with the ATLAS detector

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    Charged-particle distributions at low transverse momentum in s=13\sqrt{s} = 13 TeV pppp interactions measured with the ATLAS detector at the LHC

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    Measurement of jet fragmentation in Pb+Pb and pppp collisions at sNN=2.76\sqrt{{s_\mathrm{NN}}} = 2.76 TeV with the ATLAS detector at the LHC

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    Search for new phenomena in events containing a same-flavour opposite-sign dilepton pair, jets, and large missing transverse momentum in s=\sqrt{s}= 13 pppp collisions with the ATLAS detector

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    Search for single production of vector-like quarks decaying into Wb in pp collisions at s=8\sqrt{s} = 8 TeV with the ATLAS detector

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