1,762 research outputs found

    ρ\rho Polarization and `Model Independent' Extraction of Vub/Vcd|V_{ub}|/|V_{cd}| from DρνD\to\rho\ell\nu and BρνB\to\rho\ell\nu

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    We briefly discuss the predictions of the heavy quark effective theory for the semileptonic decays of a heavy pseudoscalar to a light one, or to a light vector meson. We point out that measurement of combinations of differential helicity decay rates at Cleo-c and the BB factories can provide a model independent means of extracting the ratio Vub/Vcd|V_{ub}|/|V_{cd}|. We briefly discuss the corrections to this prediction.Comment: 8 pages, LaTeX, 1 figur

    Some Observations Concerning Electronic Densities, Electrostatic Potentials and Chemical Potentials

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    The hypothesis that the electronic density distribution in a molecule is qualitatively similar to the nuclear potential is shown. to be in error in at least two cases-oxirane and cubane-although it does hold true in a\u27 number of other systems. Its emphasis upon the dominant role played by electrostatic internctions with the nuclei is consistent with some approximate molecular energy formulas. However, taking the nuclear potential as an approximation to the electronic density misses the small effects that correspond to the formation of chemical bonds. It is suggested that the electronic density difference function should provide a rough picture of the local variations in the chemical potential that occur as atoms combine to form a molecule. Finally, the common practice of representing the energy and electronegativity of an interacting atom as functions only of the number of electrons associated with the atom is shown to be ina\u27dequate; some account should be taken of the changing internuclear separations

    Breakdown of scaling in neutrino and electron scattering

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    Observation of deviations from scaling in the structure functions for deep-inelastic inclusive lepton-hadron scattering may provide a test of the hypothesis that the strong interactions are described by an asymptotically free field theory. Tests not involving additional assumptions are obtained for the combinations of structure functions F2 (ep)-F2 (en), F2 (ν)-F2 (ν), and xF3(ν or ν). Neutrino and electron scattering experiments are compared as possible tests of asymptotic freedom

    Higher Order 1/m1/m Corrections at Zero Recoil

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    The general structure of the 1/m1/m corrections at zero recoil is studied. The relevant matrix elements are forward matrix elements of local higher dimensional operators and their time ordered products with higher order terms from the Lagrangian. These matrix elements may be classified in a simple way and the analysis at the non recoil point for the form factor of heavy quark currents simplifies drastically. The second order recoil corrections to the form factor hA1h_{A1} of the axial vector current, relevant for the Vcb|V_{cb}| determination from BDB \to D^* decays, are estimated to be 5%<hA11<0-5\% < h_{A1} - 1 < 0.Comment: LaTeX, 25 pages, one figure, appended after \end{document} as uu-encoded and compressed eps file, uses epsf, CERN-TH.7162/9

    Path Integrals, Density Matrices, and Information Flow with Closed Timelike Curves

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    Two formulations of quantum mechanics, inequivalent in the presence of closed timelike curves, are studied in the context of a soluable system. It illustrates how quantum field nonlinearities lead to a breakdown of unitarity, causality, and superposition using a path integral. Deutsch's density matrix approach is causal but typically destroys coherence. For each of these formulations I demonstrate that there are yet further alternatives in prescribing the handling of information flow (inequivalent to previous analyses) that have implications for any system in which unitarity or coherence are not preserved.Comment: 25 pages, phyzzx, CALT-68-188

    Hadronic Transitions among Quarkonium States in a Soft-Exchange-Approximation. Chiral Breaking and Spin Symmetry Breaking Processes

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    Although no asymptotic heavy quark spin symmetry, and even more no flavor symmetry, are expected for systems such as quarkonium, a numerical discussion shows that for some processes and in a preasymptotic region which may roughly include charmonium and bottomonium, the use of the spin-symmetry may be useful in conjunction with chiral symmetry for light hadrons (soft-exchange- approximation regime, SEA). We continue our discussion of hadronic transitions in the SEA-regime by studying in particular chiral breaking transitions such as  3P 3Pπ0~^3P' \to ~^3P\pi^0,  3Pη~^3P\eta, level splittings and transitions which break both chiral and spin symmetry, such as ψJ/ψπ0\psi ' \to J/\psi \pi^0, J/ψηJ/\psi \eta, and  1P1J/ψπ0~^1P_1 \to J/\psi \pi^0.Comment: LaTeX (style article) 19 pages, UGVA-DPT 12-80

    Estimates with an Effective Chiral Lagrangian for Heavy Mesons

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    On the basis of an effective lagrangian incorporating approximate chiral symmetry and heavy-quark spin and flavor symmetries, and by use of information on leptonic decays, we estimate the effective DDπD^\star D\pi coupling.Comment: UGVA-DPT 1992/07-779, BARI-TH/92-117 Revised version, September 1992, LaTeX (style article), 7 page

    Complete Renormalization Group Improvement-Avoiding Factorization and Renormalization Scale Dependence in QCD Predictions

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    For moments of leptoproduction structure functions we show that all dependence on the renormalization and factorization scales disappears, provided that all the ultraviolet logarithms involving the physical energy scale Q are completely resummed. The approach is closely related to Grunberg's method of Effective Charges. A direct and simple method for extracting the universal dimensional transmutation parameter of QCD from experimental data is advocated.Comment: 16 pages, no figure

    Reinstatement of "germinal epithelium" of the ovary

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    BACKGROUND: The existing dogma that the former term ovarian "germinal epithelium" resulted from a mistaken belief that it could give rise to new germ cells is now strongly challenged. DISCUSSION: Two years ago, a research group of the University of Tennessee led by Antonin Bukovsky successfully demonstrated the oogenic process from the human ovarian covering epithelium now commonly called the ovarian surface epithelium. They showed the new oocyte with zona pellucida and granulosa cells, both originated from the surface epithelium arising from mesenchymal cells in the tunica albuginea, and stressed that the human ovary could form primary follicles throughout the reproductive period. This gives a big impact not only to the field of reproductive medicine, but also to the oncologic area. The surface epithelium is regarded as the major source of ovarian cancers, and most of the neoplasms exhibit the histology resembling müllerian epithelia. Since the differentiating capability of the surface epithelium has now expanded, the histologic range of the neoplasms in this category may extend to include both germ cell tumors and sex cord-stromal cell tumors. SUMMARY: Since the oogenic capability of ovarian surface cells has been proven, it is now believed that the oocytes can originate from them. The term "germinal epithelium", hence, might reasonably be reinstated
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