17,234 research outputs found

    Dynamics of hadron strong production and decay

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    We generalize results of lattice QCD to determine the spin-dependent symmetries and factorization properties of meson production in OZI allowed processes. This explains some conjectures previously made in the literature about axial meson decays and gives predictions for exclusive decays of vector charmonia, including ways of establishing the structure of Y(4260) and Y(4325) from their S-wave decays. Factorization gives a selection rule which forbids e+e−→D∗D2e^+e^- \to D^* D_2 near threshold with the tensor meson in helicity 2. The relations among amplitudes for double charmonia production \e^+e^-\to \psi\chi_{0,1,2} are expected to differ from the analagous relations among light flavour production such as \e^+e^-\to \omega f_{0,1,2}.Comment: 13 pages; journal versio

    The 2^-+ assignment for the X(3872)

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    Very recently the BaBar collaboration has put forward a claim that the X(3872) is not a 1^++ resonance, as most of the phenomenological work on the subject was relying on, but rather a 2^-+ one. We examine the consequences of this quantum number assignment for the solution of the X(3872) puzzle. The molecular interpretation appears less likely, and the conventional charmonium interpretation should be reconsidered. There are several well-known difficulties with this interpretation, to which we add a new one: the production cross section at CDF is predicted to be much smaller than that observed. We also confirm, using a relativistic string model, the conclusion from potential models that the mass of the state is not consistent with expectations. In the tetraquark interpretation the 2^-+ assignment implies a rich spectrum of partner states, although the X(3872) may be among the few which are narrow enough to be observable.Comment: 18 pages, 6 figures, 4 tables; minor style corrections. Version to appear in PR

    ANISAP: A three-dimensional finite element program for laminated composites subjected to mechanical loading

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    ANISAP is a 3-D finite element FORTRAN 77 computer code for linear elastic, small strain, analysis of laminated composites with arbitrary geometry including free edges and holes. Individual layers may be isotropic or transversely isotropic in material principal coordinates; individual layers may be rotated off-axis about a global z-axis. The laminate may be a hybrid. Three different isoparametric elements, variable order of gaussian integration, calculation of stresses at element boundaries, and loading by either nodal displacement of forces are included in the program capability. Post processing capability includes failure analysis using the tensor polynominal failure criterion

    ChromaStarPy: A stellar atmosphere and spectrum modeling and visualization lab in python

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    We announce ChromaStarPy, an integrated general stellar atmospheric modeling and spectrum synthesis code written entirely in python V. 3. ChromaStarPy is a direct port of the ChromaStarServer (CSServ) Java modeling code described in earlier papers in this series, and many of the associated JavaScript (JS) post-processing procedures have been ported and incorporated into CSPy so that students have access to ready-made "data products". A python integrated development environment (IDE) allows a student in a more advanced course to experiment with the code and to graphically visualize intermediate and final results, ad hoc, as they are running it. CSPy allows students and researchers to compare modeled to observed spectra in the same IDE in which they are processing observational data, while having complete control over the stellar parameters affecting the synthetic spectra. We also take the opportunity to describe improvements that have been made to the related codes, ChromaStar (CS), CSServ and ChromaStarDB (CSDB) that, where relevant, have also been incorporated into CSPy. The application may be found at the home page of the OpenStars project: http://www.ap.smu.ca/~ishort/OpenStars/ .Comment: See DOI zenodo.1095687. Accepted for publication in The Astrophysical Journa

    The momentum distribution of J/psi in B decays

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    The discrepancy between theory and data in the momentum distribution of slow J/psi in B decays has been several times addressed as a puzzle. Using the most recent results on exclusive B decays into J/psi and heavy kaons or exotic mesons and reconsidering the non-relativistic-QCD calculation of the color octet fragmentation component, we show that an improvement in the comparison between data and theory can be obtained. There is still room for a better fit to data and this may imply that new exotic mesons of the XYZ kind have yet to be discovered.Comment: 4 pages, 2 figures, 2 tables. To appear in Physical Review

    Resonant inelastic x-ray scattering study of charge excitations in La2CuO4

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    We report a resonant inelastic x-ray scattering study of the dispersion relations of charge transfer excitations in insulating La2_2CuO4_4. These data reveal two peaks, both of which show two-dimensional characteristics. The lowest energy excitation has a gap energy of ∼2.2\sim 2.2 eV at the zone center, and a dispersion of ∼1\sim 1 eV. The spectral weight of this mode becomes dramatically smaller around (π\pi, π\pi). The second peak shows a smaller dispersion (∼0.5\sim 0.5 eV) with a zone-center energy of ∼3.9\sim 3.9 eV. We argue that these are both highly dispersive exciton modes damped by the presence of the electron-hole continuum.Comment: 5 pages, 3 figure

    On equivariant characteristic ideals of real classes

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    Let pp be an odd prime, F/QF/{\Bbb Q} an abelian totally real number field, F∞/FF_\infty/F its cyclotomic Zp{\Bbb Z}_p-extension, G∞=Gal(F∞/Q),G_\infty = Gal (F_\infty / {\Bbb Q}), A=Zp[[G∞]].{\Bbb A} = {\Bbb Z}_p [[G_\infty]]. We give an explicit description of the equivariant characteristic ideal of HIw2(F∞,Zp(m))H^2_{Iw} (F_\infty, {\Bbb Z}_p(m)) over A{\Bbb A} for all odd m∈Zm \in {\Bbb Z} by applying M. Witte's formulation of an equivariant main conjecture (or "limit theorem") due to Burns and Greither. This could shed some light on Greenberg's conjecture on the vanishing of the λ\lambda-invariant of $F_\infty/F.

    High-Definition Optical Coherence Tomography for the in vivo Detection of Demodex Mites

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    Background: Demodex mites are involved in different skin diseases and are commonly detected by skin scrape tests or superficial biopsies. A new high-definition optical coherence tomography (HD-OCT) with high lateral and axial resolution in a horizontal (en-face) and vertical (slice) imaging mode might offer the possibility of noninvasive and fast in vivo examination of demodex mites. Methods: Twenty patients with demodex-related skin diseases and 20 age- and gender-matched healthy controls were examined by HD-OCT. Mites per follicle and follicles per field of view were counted and compared to skin scrape tests. Results: HD-OCT images depicted mites in the en-face mode as bright round dots in groups of 3-5 mites per hair follicle. In the patients with demodex-related disease, a mean number of 3.4 mites per follicle were detected with a mean number of 2.9 infested follicles per area of view compared to a mean of 0.6 mites in 0.4 infested follicles in the controls. The skin scrape tests were negative in 21% of the patients. Conclusion: The innovative HD-OCT enables fast and noninvasive in vivo recognition of demodex mites and might become a useful tool in the diagnosis and treatment monitoring of demodex-related skin diseases. Copyright (C) 2012 S. Karger AG, Base

    Strong optical force induced by morphology dependent resonances

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    We consider the resonant optical force acting on a pair of transparent microspheres by the excitation of the Morphology Dependent Resonance (MDR). The bonding and anti-bonding modes of the MDR correspond to strong attractions and repulsions respectively. The dependence of the force on separation and the role of absorption are discussed. At resonance, the force can be enhanced by orders of magnitude so that it will dominate over other relevant forces. We find that a stable binding configuration can be induced by the resonant optical force.Comment: 4 pages, 4 figure
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