4,213 research outputs found

    Anomalous trilinear and quartic WWő≥WW\gamma, WWő≥ő≥WW\gamma\gamma, ZZő≥ZZ\gamma and ZZő≥ő≥ZZ\gamma\gamma couplings in photon induced processes at the LHC

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    We first report on possible measurements at the LHC using the first data and a luminosity of 10 pb‚ąí1^{-1} of WW and ZZ pair production via two-photon exchange. This measurement allows in particular to increase the present sensitivity on WWő≥ő≥WW\gamma \gamma and ZZő≥ő≥ZZ\gamma \gamma quartic anomalous couplings from the LEP experiments by almost three orders of magnitude. We also discuss the possible improvements on quartic and trilinear anomalous couplings at high luminosity at the LHC using new forward proton taggers to be installed at 220 and 420 m from the CMS or ATLAS detectors.Comment: Proceedings of the EPS 2009 conference, Cracow, July 200

    Anomalous quartic WWgamma gamma, ZZgamma gamma, and trilinear WWgamma couplings in two-photon processes at high luminosity at the LHC

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    We study the W/Z pair production via two-photon exchange at the LHC and give the sensitivities on trilinear and quartic gauge anomalous couplings between photons and W/Z bosons for an integrated luminosity of 30 and 200 fb^{-1}. For simplicity and to obtain lower backgrounds, only the leptonic decays of the electroweak bosons are considered.Comment: 22 pages, 17 figures, sumitted to Phys. Rev.

    Enhanced ferroelectric polarization by induced Dy spin-order in multiferroic DyMnO3

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    Neutron powder diffraction and single crystal x-ray resonant magnetic scattering measurements suggest that Dy plays an active role in enhancing the ferroelectric polarization in multiferroic DyMnO3 above TNDy = 6.5 K. We observe the evolution of an incommensurate ordering of Dy moments with the same periodicity as the Mn spiral ordering. It closely tracks the evolution of the ferroelectric polarization which reaches a maximum value of 0.2 muC/m^2. Below TNDy, where Dy spins order commensurately, the polarization decreases to values similar for those of TbMnO3

    Anisotropic interactions opposing magnetocrystalline anisotropy in Sr3_3NiIrO6_6

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    We report our investigation of the electronic and magnetic excitations of Sr3_3NiIrO6_6 by resonant inelastic x-ray scattering at the Ir L3_3 edge. The intra-t2gt_{2g} electronic transitions are analyzed using an atomic model, including spin-orbit coupling and trigonal distortion of the IrO6_6 octahedron, confronted to {\it ab initio} quantum chemistry calculations. The Ir spin-orbital entanglement is quantified and its implication on the magnetic properties, in particular in inducing highly anisotropic magnetic interactions, is highlighted. These are included in the spin-wave model proposed to account for the dispersionless magnetic excitation that we observe at 90 meV. By counterbalancing the strong Ni2+^{2+} easy-plane anisotropy that manifests itself at high temperature, the anisotropy of the interactions finally leads to the remarkable easy-axis magnetism reported in this material at low temperature

    Magnetic order in the frustrated Ising-like chain compound Sr3_3NiIrO6_6

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    We have studied the field and temperature dependence of the magnetization of single crystals of Sr3NiIrO6. These measurements evidence the presence of an easy axis of anisotropy and two anomalies in the magnetic susceptibility. Neutron powder diffraction realized on a polycrystalline sample reveals the emergence of magnetic reflections below 75 K with magnetic propagation vector k ~ (0, 0, 1), undetected in previous neutron studies [T.N. Nguyen and H.-C zur Loye, J. Solid State Chem., 117, 300 (1995)]. The nature of the magnetic ground state, and the presence of two anomalies common to this family of material, are discussed on the basis of the results obtained by neutron diffraction, magnetization measurements, and symmetry arguments

    Trisomy 19 ependymoma, a newly recognized genetico-histological association, including clear cell ependymoma

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    Ependymal tumors constitute a clinicopathologically heterogeneous group of brain tumors. They vary in regard to their age at first symptom, localization, morphology and prognosis. Genetic data also suggests heterogeneity. We define a newly recognized subset of ependymal tumors, the trisomy 19 ependymoma. Histologically, they are compact lesions characterized by a rich branched capillary network amongst which tumoral cells are regularly distributed. When containing clear cells they are called clear cell ependymoma. Most trisomy 19 ependymomas are supratentorial WHO grade III tumors of the young. Genetically, they are associated with trisomy 19, and frequently with a deletion of 13q21.31-31.2, three copies of 11q13.3-13.4, and/or deletions on chromosome 9. These altered chromosomal regions are indicative of genes and pathways involved in trisomy 19 ependymoma tumorigenesis. Recognition of this genetico-histological entity allows better understanding and dissection of ependymal tumors

    Prediction for new magnetoelectric fluorides

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    We use symmetry considerations in order to predict new magnetoelectric fluorides. In addition to these magnetoelectric properties, we discuss among these fluorides the ones susceptible to present multiferroic properties. We emphasize that several materials present ferromagnetic properties. This ferromagnetism should enhance the interplay between magnetic and dielectric properties in these materials.Comment: 12 pages, 4 figures, To appear in Journal of Physics: Condensed Matte

    Detection of negative ions in glow discharge mass spectrometry for analysis of solid specimens

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    A new method is presented for elemental and molecular analysis of halogen-containing samples by glow discharge time-of-flight mass spectrometry, consisting of detection of negative ions from a pulsed RF glow discharge in argon. Analyte signals are mainly extracted from the afterglow regime of the discharge, where the cross section for electron attachment increases. The formation of negative ions from sputtering of metals and metal oxides is compared with that for positive ions. It is shown that the negative ion signals of F(-) and TaO(2)F(-) are enhanced relative to positive ion signals and can be used to study the distribution of a tantalum fluoride layer within the anodized tantala layer. Further, comparison is made with data obtained using glow-discharge optical emission spectroscopy, where elemental fluorine can only be detected using a neon plasma. The ionization mechanisms responsible for the formation of negative ions in glow discharge time-of-flight mass spectrometry are briefly discussed
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