87 research outputs found

    Comment on Neutron-Proton Spin-Correlation Parameter A_{ZZ} at 68 Mev

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    We present two arguments indicating that the large value for the ϵ1\epsilon_1 mixing parameter at 50 MeV, which the Basel group extracted from their recent AzzA_{zz} measurement, may be incorrect. First, there are nucleon-nucleon (NN) potentials which predict the ϵ1\epsilon_1 at 50 MeV substantially below the Basel value and reproduce the Basel AzzA_{zz} data accurately. Second, the large value for ϵ1\epsilon_1 at 50 MeV proposed by the Basel group can only be explained by a model for the NN interaction which is very unrealistic (no ρ\rho-meson and essentially a point-like πNN\pi NN vertex) and overpredicts the ϵ1\epsilon_1 in the energy range where it is well determined (150--500 MeV) by a factor of two.Comment: 6 pages text (LaTex) and 2 figures (paper, will be faxed upon request), UI-NTH-930

    3-He(p,pp)d and 3-He(p,pp)d* Reactions at 136 MeV

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    This work was supported by National Science Foundation Grant PHY 76-84033 and Indiana Universit

    In-medium nucleon-nucleon potentials in configuration space

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    Based on the thermodynamic Green function approach two-nucleon correlations in nuclear matter at finite temperatures are revisited. To this end, we derive phase equivalent effective rr-space potentials that include the effect of the Pauli blocking at a given temperature and density. These potentials enter into a Schr\"odinger equation that is the rr-space representation of the Galitskii-Feynman equation for two nucleons. We explore the analytical structure of the equation in the complex kk-plane by means of Jost functions. We find that despite the Mott effect the correlation with deuteron quantum numbers are manifested as antibound states, i.e., as zeros of the Jost function on the negative imaginary axis of the complex momentum space. The analysis presented here is also suited for Coulombic systems.Comment: 6 pages, 1 table, 4 figure

    Charge-Dependence of the Nucleon-Nucleon Interaction

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    Based upon the Bonn meson-exchange-model for the nucleon-nucleon (NNNN) interaction, we calculate the charge-independence breaking (CIB) of the NNNN interaction due to pion-mass splitting. Besides the one-pion-exchange (OPE), we take into account the 2π2\pi-exchange model and contributions from three and four irreducible pion exchanges. We calculate the CIB differences in the 1S0^1S_0 effective range parameters as well as phase shift differences for partial waves up to total angular momentum J=4 and laboratory energies below 300 MeV. We find that the CIB effect from OPE dominates in all partial waves. However, the CIB effects from the 2π2\pi model are noticable up to D-waves and amount to about 40% of the OPE CIB-contribution in some partial waves, at 300 MeV. The effects from 3π\pi and 4π\pi contributions are negligible except in 1S0^1S_0 and 3P2^3P_2.Comment: 12 pages, RevTex, 14 figure

    Investigation of the nucleon-nucleon tensor force in the three-nucleon system

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    Proton-deuteron elastic scattering has been investigated at Ep =22.7 MeV by comparison of rigorous Faddeev calculations with experimental results. The observable most sensitive to the tensor force is the nucleon-nucleon polarization transfer coefficient Kyy'. The new angular distribution of Kyy' clearly favours the tensor force of the Bonn A potential, which is weaker than the one of the Paris potential.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28425/1/0000208.pd

    Charge-Asymmetry of the Nucleon-Nucleon Interaction

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    Based upon the Bonn meson-exchange model for the nucleon-nucleon (NNNN) interaction, we study systematically the charge-symmetry-breaking (CSB) of the NNNN interaction due to nucleon mass splitting. Particular attention is payed to CSB generated by the 2π2\pi-exchange contribution to the NNNN interaction, πρ\pi\rho diagrams, and other multi-meson-exchanges. We calculate the CSB differences in the 1S0^1S_0 effective range parameters as well as phase shift differences in SS, PP and higher partial waves up to 300 MeV lab. energy. We find a total CSB difference in the singlet scattering length of 1.6 fm which explains the empirical value accurately. The corresponding CSB phase-shift differences are appreciable at low energy in the 1S0^1S_0 state. In the other partial waves, the CSB splitting of the phase shifts is small and increases with energy, with typical values in the order of 0.1 deg at 300 MeV in PP and DD waves.Comment: 11 pages, RevTex, 14 figure

    Survey of attitudes, materials and methods employed in endodontic treatment by general dental practitioners in North Jordan

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    BACKGROUND: General dental practitioners provide the majority of endodontic treatment in Jordan. The aim of this study was to gather information on the methods, materials and attitudes employed in root canal treatment by dentists in North Jordan, in order to evaluate and improve the quality of current practice. METHODS: A questionnaire was posted to all registered general dental practitioners working in private practice in Irbid Governate in North Jordan (n = 181). The questionnaire included information on methods, materials and techniques used in endodontic treatment. RESULTS: Reply rate was 72% (n = 131). The results demonstrated that only five dentists used rubber dam occasionally and not routinely. The majority used cotton rolls for isolation solely or in combination with a high volume saliva ejector (n = 116). The most widely used irrigants were sodium hypochlorite and hydrogen peroxide, which were used by 32.9% (n = 43) and 33.6% (n = 44) of the respondents, respectively. Forty eight percent of the respondents (n = 61) used the cold lateral condensation technique for canal obturation, 31.3% (n = 41) used single cone, 9.9% (n = 13) used vertical condensation and 12.2% (n = 16) used paste or cement only for the obturation. The majority used zinc oxide eugenol as a sealer (72.5%). All, but one, respondents used hand instruments for canal preparation and the technique of choice was step back (52.7%). More than 50% (n = 70) of the dentists took one radiograph for determining the working length, whilst 22.9% (n = 30) did not take any radiograph at all. Most practitioners performed treatment in three visits for teeth with two or more root canals, and in two visits for teeth with a single root canal. CONCLUSIONS: This study indicates that dentists practicing in North Jordan do not comply with international quality standards and do not use recently introduced techniques. Many clinicians never take a radiograph for determining the working length and never used rubber dam or intra-canal medicaments
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