3,679 research outputs found

    Charm (and Beauty) Production at the Tevatron

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    We present recent results on heavy flavour production at Tevatron Run II for typically ~1/fb of analysed proton-antiproton data at a c.m. energy of 1.96 TeV. This includes results on single and correlated open charm and bottom cross sections, charm pair production kinematics, J/psi, psi(2S) and chi cross sections and polarisation measurements in J/psi, psi(2S), Upsilon(1S), and Upsilon(2S).Comment: To be published in the proceedings of CHARM07, Ithaca, NY, August 2007, eConf C07080

    Black hole shadows in fourth-order conformal Weyl gravity

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    We calculate the characteristics of the "black hole shadow" for a rotating, neutral black hole in fourth-order conformal Weyl gravity. It is shown that the morphology is not significantly affected by the underlying framework, except for very large masses. Conformal gravity black hole shadows would also significantly differ from their general relativistic counterparts if the values of the main conformal gravity parameters, Îł\gamma and Îş\kappa, were increased by several orders of magnitude. Such increased values for Îł\gamma and Îş\kappa are currently ruled out by gravitational phenomenology. Therefore, it is unlikely that these differences in black hole shadows will be detected in future observations, carried out by the Event Horizon Telescope or other such experiments.Comment: 21 pages, including 2 figures. Minor corrections and references added. Final version to appear in the Canadian Journal of Physic

    23. Areogeophysical Investigations over the Bowers Mountains, North Victoria Land; Antarctica

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    Three-body effects in the Hoyle-state decay

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    We use a sequential RR-matrix model to describe the breakup of the Hoyle state into three α\alpha particles via the ground state of 8Be^8\mathrm{Be}. It is shown that even in a sequential picture, features resembling a direct breakup branch appear in the phase-space distribution of the α\alpha particles. We construct a toy model to describe the Coulomb interaction in the three-body final state and its effects on the decay spectrum are investigated. The framework is also used to predict the phase-space distribution of the α\alpha particles emitted in a direct breakup of the Hoyle state and the possibility of interference between a direct and sequential branch is discussed. Our numerical results are compared to the current upper limit on the direct decay branch determined in recent experiments

    Black hole shadows in fourth-order conformal Weyl gravity

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    We calculate the characteristics of the “black hole shadow” for a rotating, neutral black hole in fourth-order conformal Weyl gravity. It is shown that the morphology is not significantly affected by the underlying framework, except for very large masses. Conformal gravity black hole shadows would also significantly differ from their general relativistic counterparts if the values of the main conformal gravity parameters, γ and κ, were increased by several orders of magnitude. Such increased values for γ and κ are currently ruled out by gravitational phenomenology. Therefore, it is unlikely that these differences in black hole shadows will be detected in future observations, carried out by the Event Horizon Telescope or other such experiments

    Coherent Transport through an interacting double quantum dot: Beyond sequential tunneling

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    Various causes for negative differential conductance in transport through an interacting double quantum dot are investigated. Particular focus is given to the interplay between the renormalization of the energy levels due to the coupling to the leads and the decoherence of the states. The calculations are performed within a basis of many-particle eigenstates and we consider the dynamics given by the von Neumann-equation taking into account also processes beyond sequential tunneling. A systematic comparison between the levels of approximation and also with different formalisms is performed. It is found that the current is qualitatively well described by sequential processes as long as the temperature is larger than the level broadening induced by the contacts.Comment: 11 pages, 5 figures included in tex

    Superconducting Films for Absorber-Coupled MKID Detectors for Sub-Millimeter and Far-Infrared Astronomy

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    We describe measurements of the properties, at dc, gigahertz, and terahertz frequencies, of thin (10 nm) aluminum films with 10 ohm/{rm square}$ normal state sheet resistance. Such films can be applied to construct microwave kinetic inductance detector arrays for submillimeter and far-infrared astronomical applications in which incident power excites quasiparticles directly in a superconducting resonator that is configured to present a matched-impedance to the high frequency radiation being detected. For films 10 nm thick, we report normal state sheet resistance, resistance-temperature curves for the superconducting transition, quality factor and kinetic inductance fraction for microwave resonators made from patterned films, and terahertz measurements of sheet impedance measured with a Fourier Transform Spectrometer. We compare properties with similar resonators made from niobium 600 nm thick
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