45,834 research outputs found

    Contribution of b→sggb \to sgg through the QCD anomaly in exclusive decays B±→(η′,η)(K±,K∗±)B^{\pm}\to (\eta^{\prime},\eta)(K^{\pm}, K^{*\pm}) and B0→(η′,η)(K0,K∗0)B^{0}\to (\eta^{\prime},\eta)(K^{0},K^{*0})

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    We compute the decay rates for the exclusive decays B±→(η′,η)(K±,K∗±)B^{\pm} \to (\eta^{\prime},\eta) (K^{\pm}, K^{*\pm}) and B0→(η′,η)(K0,K∗0)B^{0}\to (\eta^{\prime},\eta) (K^{0}, K^{*0}) in a QCD-improved factorization framework by including the contribution from the process b→sgg→s(η′,η)b\to sgg \to s (\eta^{\prime}, \eta) through the QCD anomaly. This method provides an alternative estimate of the contribution b→sccˉ→s(η,η′)b \to s c\bar{c} \to s(\eta,\eta^\prime) to these decays as compared to the one using the intrinsic charm content of the η′\eta^{\prime} and η\eta mesons determined through the decays J/ψ→(η,η′,ηc)γJ/\psi \to (\eta,\eta^\prime ,\eta_c) \gamma. The resulting branching ratios are compared with the CLEO data on B±→η′K±B^{\pm} \to \eta^{\prime} K^{\pm} and B0→η′K0B^{0} \to \eta^{\prime} K^{0} and predictions are made for the rest.Comment: 16 pages including 4 postscript figures; uses epsfig. The most recent branching ratios from CLEO, ref. [5], are taken into account. The theory part is unchange

    Building Proteins in a Day: Efficient 3D Molecular Reconstruction

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    Discovering the 3D atomic structure of molecules such as proteins and viruses is a fundamental research problem in biology and medicine. Electron Cryomicroscopy (Cryo-EM) is a promising vision-based technique for structure estimation which attempts to reconstruct 3D structures from 2D images. This paper addresses the challenging problem of 3D reconstruction from 2D Cryo-EM images. A new framework for estimation is introduced which relies on modern stochastic optimization techniques to scale to large datasets. We also introduce a novel technique which reduces the cost of evaluating the objective function during optimization by over five orders or magnitude. The net result is an approach capable of estimating 3D molecular structure from large scale datasets in about a day on a single workstation.Comment: To be presented at IEEE Conference on Computer Vision and Pattern Recognition (CVPR) 201

    Submm-bright QSOs at z~2: signposts of co-evolution at high z

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    We have assembled a sample of 5 X-ray and submm-luminous z~2 QSOs which are therefore both growing their central black holes through accretion and forming stars copiously at a critical epoch. Hence, they are good laboratories to investigate the co-evolution of star formation and AGN. We have performed a preliminary analysis of the AGN and SF contributions to their UV-to-FIR SEDs, fitting them with simple direct (disk), reprocessed (torus) and star formation components. All three are required by the data and hence we confirm that these objects are undergoing strong star formation in their host galaxies at rates 500-2000 Msun/y. Estimates of their covering factors are between about 30 and 90%. In the future, we will assess the dependence of these results on the particular models used for the components and relate their observed properties to the intrinsice of the central engine and the SF material, as well as their relevance for AGN-galaxy coevolution.Comment: 6 pages, 2 figures, contributed talk to "Nuclei of Seyfert galaxies and QSOs - Central engine & conditions of star formation" November 6-8, 2012. MPIfR, Bonn, Germany. Po

    Squeezed states: A geometric framework

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    A general definition of squeezed states is proposed and its main features are illustrated through a discussion of the standard optical coherent states represented by 'Gaussian pure states'. The set-up involves representations of groups on Hilbert spaces over homogeneous spaces of the group, and relies on the construction of a square integrable (coherent state) group representation modulo a subgroup. This construction depends upon a choice of a Borel section which has a certain permissible arbitrariness in its selection; this freedom is attributable to a squeezing of the defining coherent states of the representation, and corresponds in this way to a sort of gauging
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