84 research outputs found

    Quantum Mechanical Approaches for Piezoelectricity Study in Perovskites

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    In this chapter, we show the procedures we have been used to theoretically investigate the piezoelectric effects in perovskites. The construction of extended basis sets using the generator coordinate Hartree-Fock (GCHF) method is shown, as well as the strategies used to contract extended basis sets and to evaluate their quality in molecular calculations. Besides, we show adequate procedures to choice polarization and diffuse functions to best represent the studied crystal. In addition, we also discuss conditions under which GCHF basis sets and standard basis sets from literature can be used to theoretical investigation of piezoelectricity in perovskites. We finalize the chapter presenting and discussing the results for investigations of piezoelectricity with standard basis sets for barium and lanthanum titanates. To conclude, we present evidences that BaTiO3 and LaTiO3 may have piezoelectric properties caused by electrostatic interactions

    Combined search for anomalous pseudoscalar HW couplings in VH(H -> b(b)over-bar) production and H -> VV decay

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    Measurement of the Z gamma -> nu(nu)over-bar gamma production cross section in pp collisions at root s=8 TeV and limits on anomalous ZZ gamma and Z gamma gamma trilinear gauge boson couplings

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    Search for lepton flavour violating decays of the Higgs boson to eτ and eμ in proton–proton collisions at √s=8 TeV

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    A direct search for lepton flavour violating decays of the Higgs boson (H) in the H→eτH→eτ and H→eμH→eμ channels is described. The data sample used in the search was collected in proton–proton collisions at View the MathML sources=8 TeV with the CMS detector at the LHC and corresponds to an integrated luminosity of 19.7 fb−1. No evidence is found for lepton flavour violating decays in either final state. Upper limits on the branching fractions, B(H→eτ)<0.69%B(H→eτ)<0.69% and B(H→eμ)<0.035%B(H→eμ)<0.035%, are set at the 95% confidence level. The constraint set on B(H→eτ)B(H→eτ) is an order of magnitude more stringent than the existing indirect limits. The limits are used to constrain the corresponding flavour violating Yukawa couplings, absent in the standard model

    Measurement of dijet azimuthal decorrelation in pp collisions at root s=8 TeV

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    Measurement of the tt¯ production cross section in the all-jets final state in pp collisions at √s = 8 TeV

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    The cross section for tt¯ production in the all-jets final state is measured in pp collisions at a centre-of-mass energy of 8 TeV at the LHC with the CMS detector, in data corresponding to an integrated luminosity of 18.4 fb-1 . The inclusive cross section is found to be 275.6±6.1(stat)±37.8(syst)±7.2(lumi) \,pb . The normalized differential cross sections are measured as a function of the top quark transverse momenta, pT , and compared to predictions from quantum chromodynamics. The results are reported at detector, parton, and particle levels. In all cases, the measured top quark pT spectra are significantly softer than theoretical predictions

    Pseudorapidity dependence of long-range two-particle correlations in pPb collisions at root sNN=5.02 TeV

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    Search for supersymmetry in electroweak production with photons and large missing transverse energy in pp collisions at √s=8TeV

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    Results are reported from a search for supersymmetry with gauge-mediated supersymmetry breaking in electroweak production. Final states with photons and large missing transverse energy ( ETmiss ) were examined. The data sample was collected in pp collisions at s=8TeV with the CMS detector at the LHC and corresponds to 7.4 fb−1 . The analysis focuses on scenarios in which the lightest neutralino has bino- or wino-like components, resulting in decays to photons and gravitinos, where the gravitinos escape undetected. The data were obtained using a specially designed trigger with dedicated low thresholds, providing good sensitivity to signatures with photons, ETmiss , and low hadronic energy. No excess of events over the standard model expectation is observed. The results are interpreted using the model of general gauge mediation. With the wino mass fixed at 10 GeV above that of the bino, wino masses below 710 GeV are excluded at 95% confidence level. Constraints are also set in the context of two simplified models, for which the analysis sets the lowest cross section limits on the electroweak production of supersymmetric particles

    Measurement of t(t)over-bar production with additional jet activity, including b quark jets, in the dilepton decay channel using pp collisions at root s=8TeV

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    Measurement of the t(t)over-bar production cross section in the all-jets final state in pp collisions at root s=8TeV

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