4,294 research outputs found

    Darwin-Foldy term and proton charge radius

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    In this contribution we study the Dirac equation for a finite size proton in an external electric field with explicit introduction of Dirac-Pauli form factors. Our aim is twofold. On the one hand, we wish to study whether our conclusions regarding the exact cancellation between Dirac form factor and Foldy term contributions occurring for the neutron still hold for the proton. On the other hand, we wish to clearly illustrate some of the specific features of the description of a composite particle like the proton with the Dirac equation.Comment: contribution to XVIIth European Conference of Few-Body Problems in Physics, Evora, Portugal Sept 2000, to be published in Nucl. Phys.

    Meson PVV Interactions are determined by Quark Loops

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    We show that all abnormal parity three-body meson interactions can be adequately described by quark loops, evaluated at zero external momentum, with couplings determined by U(Nf)U(N_f) symmetry. We focus primarily on radiative meson decays which involve one pseudoscalar. The agreement with experiment for non-rare decays is surprisingly good and requires very few parameters, namely the coupling constants gπqqg_{\pi qq} and gρqqg_{\rho qq} and some mixing angles. This agreement extends to some three-body decays that are dominated by pion pairs in a P-wave state.Comment: 21 pages, Revtex, one figur

    Vector Meson Dominance and Rho-Omega Mixing

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    The scale of a phenomenologically successful charge-symmetry-violating nucleon-nucleon interaction, that attributed to meson exchange with a ΔI=1\Delta I =1 rho-omega transition, is set by the Coleman-Glashow SU(2) breaking tadpole mechanism. A single tadpole scale has been obtained from symmetry arguments, electromagnetic meson and baryon measured mass splittings, and the observed isospin violating (ΔI=1\Delta I=1) decay ωπ+π\omega \to \pi^+\pi^-. The hadronic realization of this tadpole mechanism lies in the I=1I = 1 a0a_0 scalar meson. We show that measured hadronic and two-photon widths of the a0a_0 meson, with the aid of the Vector Meson Dominance model, recover the universal Coleman-Glashow tadpole scale.Comment: 18 pages, 2 figures, to appear in Physical Review

    Momentum and Coordinate Space Three-nucleon Potentials

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    In this paper we give explicit formulae in momentum and coordinate space for the three-nucleon potentials due to ρ\rho and π\pi meson exchange, derived from off-mass-shell meson-nucleon scattering amplitudes which are constrained by the symmetries of QCD and by the experimental data. Those potentials have already been applied to nuclear matter calculations. Here we display additional terms which appear to be the most important for nuclear structure. The potentials are decomposed in a way that separates the contributions of different physical mechanisms involved in the meson-nucleon amplitudes. The same type of decomposition is presented for the ππ\pi - \pi TM force: the Δ\Delta, the chiral symmetry breaking and the nucleon pair terms are isolated.Comment: LATEX, 33 pages, 3 figures (available as postscript files upon request

    Off-Mass-Shell π\piN Scattering and ppppπ0pp \to pp \pi^0

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    We adapt the off-shell π\piN amplitude of the Tucson-Melbourne three-body force to the half-off-shell amplitude of the pion rescattering contribution to ppppπ0pp \to pp \pi^0 near threshold. This {\em pion} rescattering contribution, together with the impulse term, provides a good description of the data when the half-off-shell amplitude is linked to the phenomenological invariant amplitudes obtained from meson factory π\piN scattering data.Comment: 3 pages, contributed to STORRI99, Bloomington, Indiana, September 199

    RESULTS OF THE RURAL CASS COUNTY BUSINESS AND SERVICES PREFERENCE SURVEY

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    Changing demographics in rural and urban North Dakota have provided both opportunities and challenges for rural communities. Cass County boasts the state's largest and fastest growing urban center, but the impact of the county's growth extends beyond the Fargo-West Fargo city limits. Towns like Casselton, Horace, and Kindred have experienced substantial changes not only in the number of residents, but also in the composition of households and their business and service needs and preferences. To address these questions, the Rural Cass County Business and Services Preference Survey was designed to identify and quantify residents' perceptions on a variety of issues. This report details respondents' perceptions on quality of life issues, business and service patronization, as well as describes some basic demographic characteristics of rural Cass County residents.rural development, rural Cass County, population growth, Community/Rural/Urban Development,

    Channel and noise variance estimation and tracking algorithms for unique-word based single-carrier systems

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