1,527 research outputs found

    Deuteron Dipole Polarizabilities and Sum Rules

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    The scalar, vector, and tensor components of the (generalized) deuteron electric polarizability are calculated, as well as their logarithmic modifications. Several of these quantities arise in the treatment of the nuclear corrections to the deuterium Lamb shift and the deuterium hyperfine structure. A variety of second-generation potential models are used and a (subjective) error is assigned to the calculations. The zero-range approximation is used to analyze a subset of the results, and a simple relativistic version of this approximation is developed.Comment: 14 pages, LaTex - submitted to Physical Review

    The nucleon-sigma coupling constant in QCD Sum Rules

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    The external-field QCD Sum Rules method is used to evaluate the coupling constant of the light isoscalar-scalar meson (``σ\sigma'' or \epsilon) to the nucleon. The contributions that come from the excited nucleon states and the response of the continuum threshold to the external field are calculated. The obtained value of the coupling constant is compatible with the large value required in one-boson exchange potential models of the two-nucleon interaction.Comment: 11 pages, 4 figure

    Partial Wave Analyses of the pp data alone and of the np data alone

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    We present results of the Nijmegen partial-wave analyses of all NN scattering data below Tlab = 500 MeV. We have been able to extract for the first time the important np phase shifts for both I = 0 and I = 1 from the np scattering data alone. This allows us to study the charge independence breaking between the pp and np I = 1 phases. In our analyses we obtain for the pp data chi^2_{min}/Ndf = 1.13 and for the np data chi^2_{min}/Ndf = 1.12.Comment: Report THEF-NYM 94.04, 4 pages LaTeX, one PostScript figure appended. Contribution to the 14th Few-Body Conference, May 26 - 31, Williamsburg, V

    An interacting quark-diquark model of baryons

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    A simple quark-diquark model of baryons with direct and exchange interactions is constructed. Spectrum and form factors are calculated and compared with experimental data. Advantages and disadvantages of the model are discussed.Comment: 13 pages, 3 eps-figures, accepted by Phys.Rev. C Rapid Communication

    \pi N scattering in relativistic baryon chiral perturbation theory revisited

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    We have analyzed pion-nucleon scattering using the manifestly relativistic covariant framework of Infrared Regularization up to {\cal O}(q^3) in the chiral expansion, where q is a generic small momentum. We describe the low-energy phase shifts with a similar quality as previously achieved with Heavy Baryon Chiral Perturbation Theory, \sqrt{s}\lesssim1.14 GeV. New values are provided for the {\cal O}(q^2) and {\cal O}(q^3) low-energy constants, which are compared with previous determinations. This is also the case for the scattering lengths and volumes. Finally, we have unitarized the previous amplitudes and as a result the energy range where data are reproduced increases significantly.Comment: 26 pages, 5 figures, 5 table

    Developmental Relations Between Reading Comprehension and Reading Strategies

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    Contains fulltext : 169370.pdf (publisher's version ) (Open Access)We examined the developmental relations between knowledge of reading strategies and reading comprehension in a longitudinal study of 312 Dutch children from the beginning of fourth grade to the end of fifth grade. Measures for reading comprehension, reading strategies, reading fluency, vocabulary, and working memory were administered. A structural equation model was constructed to estimate the unique relations between reading strategies and reading comprehension, while controlling for reading fluency, vocabulary, and working memory. The results showed that there was a unique effect of reading strategies on reading comprehension, and also of reading comprehension on reading strategies.16 p
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