70,036 research outputs found

    Double Beta Decay, Nuclear Structure and Physics beyond the Standard Model

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    Neutrinoless Double Beta Decay (0νββ0\nu\beta\beta) is presently the only known experiment to distinguisch between Dirac neutrinos, different from their antiparticles, and Majorana neutrinos, identical with their antiparticles. In addition 0νββ0\nu\beta\beta allows to determine the absolute scale of the neutrino masses. This is not possible with neutrino oscillations. To determine the neutrino masses one must assume, that the light Majorana neutrino exchange is the leading mechanism for 0νββ0\nu\beta\beta and that the matrix element of this transition can ba calculated reliably. The experimental 0νββ0\nu\beta\beta transition amplitude in this mechanism is a product of the light left handed effective Majorana neutrino mass and of this transition matrix element. The different methods, Quasi-particle Random Phase Approximation (QRPA), Shell Model (SM), Projected Hartree-Fock-Bogoliubov (PHFB) and Interacting Boson Model (IBM2) used in the literature and the reliability of the matrix elements in these approaches are reviewed. In the second part it is investigated how one can determine the leading mechanism or mechanisms from the data of the 0νββ0\nu\beta\beta decay in different nuclei. Explicite expressions are given for the transition matrix elements. is shown, that possible interference terms allow to test CP (Charge and Parity conjugation) violation.Comment: Contribution to the EPS conference in Eilath: "Nuclear Physics in Astrophysics 5." April 3rd to 8th. 201

    Digital computer simulation of inductor-energy-storage dc-to-dc converters with closed-loop regulators

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    The simulation of converter-controller combinations by means of a flexible digital computer program which produces output to a graphic display is discussed. The procedure is an alternative to mathematical analysis of converter systems. The types of computer programming involved in the simulation are described. Schematic diagrams, state equations, and output equations are displayed for four basic forms of inductor-energy-storage dc to dc converters. Mathematical models are developed to show the relationship of the parameters

    Electromechanical Imaging of Biological Systems with Sub-10 nm Resolution

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    Electromechanical imaging of tooth dentin and enamel has been performed with sub-10 nm resolution using piezoresponse force microscopy. Characteristic piezoelectric domain size and local protein fiber ordering in dentin have been determined. The shape of a single collagen fibril in enamel is visualized in real space and local hysteresis loops are measured. Because of the ubiquitous presence of piezoelectricity in biological systems, this approach is expected to find broad application in high-resolution studies of a wide range of biomaterials.Comment: 12 pages, 4 figures, submitted for publication in Appl. Phys. Let

    Faint emission lines in the Galactic H II regions M16, M20 and NGC 3603

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    We present deep echelle spectrophotometry of the Galactic {\hii} regions M16, M20 and NGC 3603. The data have been taken with the Very Large Telescope Ultraviolet-Visual Echelle Spectrograph in the 3100 to 10400 \AA range. We have detected more than 200 emission lines in each region. Physical conditions have been derived using different continuum and line intensity ratios. We have derived He+^{+}, C++^{++} and O++^{++} abundances from pure recombination lines as well as abundances from collisionally excited lines for a large number of ions of different elements. We have obtained consistent estimations of the temperature fluctuation parameter, {\ts}, using different methods. We also report the detection of deuterium Balmer lines up to Dδ\delta (M16) and to Dγ\gamma (M20) in the blue wings of the hydrogen lines, which excitation mechanism seems to be continuum fluorescence. The temperature fluctuations paradigm agree with the results obtained from optical CELs and the more uncertain ones from far IR fine structure CELs in NGC 3603, although, more observations covering the same volume of the nebula are necessary to obtain solid conclusions.Comment: 22 pages, 13 Tables, 7 Figures. Accepted for publication by MNRA

    High-energy gamma-ray observations of the accreting black hole V404 Cygni during its June 2015 outburst

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    We report on Fermi/Large Area Telescope observations of the accreting black hole low-mass X-ray binary V404 Cygni during its outburst in June-July 2015. Detailed analyses reveal a possible excess of γ\gamma-ray emission on 26 June 2015, with a very soft spectrum above 100100 MeV, at a position consistent with the direction of V404 Cyg (within the 95%95\% confidence region and a chance probability of 4×1044 \times 10^{-4}). This emission cannot be associated with any previously-known Fermi source. Its temporal coincidence with the brightest radio and hard X-ray flare in the lightcurve of V404 Cyg, at the end of the main active phase of its outburst, strengthens the association with V404 Cyg. If the γ\gamma-ray emission is associated with V404 Cyg, the simultaneous detection of 511511\,keV annihilation emission by INTEGRAL requires that the high-energy γ\gamma rays originate away from the corona, possibly in a Blandford-Znajek jet. The data give support to models involving a magnetically-arrested disk where a bright γ\gamma-ray jet can re-form after the occurrence of a major transient ejection seen in the radio.Comment: 5 pages, 3 figures, accepted for publication in MNRA
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