1,469 research outputs found

    Comment on "Constraints on proton structure from precision atomic physics measurements"

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    We strongly disagree with the procedure used in a recent paper to extract the Zemach moment for hydrogen.Comment: 1 page, 2 figures, revtex - submitted to Physical Review Letter

    RDWIA analysis of 12C(e,e'p) for Q^2 < 2 (GeV/c)^2

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    We analyze data for 12C(e,e'p) with Q^2 < 2 (GeV/c)^2 using the relativistic distorted-wave impulse approximation (RDWIA) based upon Dirac-Hartree wave functions. The 1p normalization extracted from data for Q^2 > 0.6 (GeV/c)^2 is approximately 0.87, independent of Q^2, which is consistent with the predicted depletion by short-range correlations. The total 1p and 1s strength for E_m < 80 MeV approaches 100% of IPSM, consistent with a continuum contribution for 30 < E_m < 80 MeV of about 12% of IPSM. Similarly, a scale factor of 1.12 brings RDWIA calculations into good agreement with 12C(e,e'p) data for transparency. We also analyzed low Q^2 data from which a recent NDWIA analysis suggested that spectroscopic factors might depend strongly upon the resolution of the probe. We find that momentum distributions for their empirical Woods-Saxon wave functions fit to low Q^2 data for parallel kinematics are too narrow to reproduce data for quasiperpendicular kinematics, especially for larger Q^2, and are partly responsible for reducing fitted normalization factors.Comment: 19 pages, 14 figures, to be submitted to PR

    Muonic Hydrogen and the Third Zemach Moment

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    We determine the third Zemach moment of hydrogen (_(2)) using only the world data on elastic electron-proton scattering. This moment dominates the O (Z alpha)^5 hadronic correction to the Lamb shift in muonic atoms. The resulting moment, _(2) = 2.71(13) fm^3, is somewhat larger than previously inferred values based on models. The contribution of that moment to the muonic hydrogen 2S level is -0.0247(12) meV.Comment: 3 pages, no figures, revtex - submitted to Physical Review

    The Soviet Presence in the Mediterranean: A Short History

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    The presence of a significant Soviet naval force in the Mediterranean seems to represent a new element in international relations

    Coulomb Sum Rule for \u3csup\u3e4\u3c/sup\u3eHE

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    We determine the Coulomb sum for 4He using the world data on 4He(e,e′) and compare the results to calculations based on realistic interactions and including two-body components in the nuclear charge operator. We find good agreement between theory and experiment when using free-nucleon form factors. The apparent reduction of the in-medium GEp implied by IA-interpretation of the L/T-ratios measured in 4He(e,e′p) and 4He(e→,e′p→) is not confirmed

    Using Electron Scattering Superscaling to predict Charge-changing Neutrino Cross Sections in Nuclei

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    Superscaling analyses of few-GeV inclusive electron scattering from nuclei are extended to include not only quasielastic processes, but now also into the region where Δ\Delta-excitation dominates. It is shown that, with reasonable assumptions about the basic nuclear scaling function extracted from data and information from other studies of the relative roles played by correlation and MEC effects, the residual strength in the resonance region can be accounted for through an extended scaling analysis. One observes scaling upon assuming that the elementary cross section by which one divides the residual to obtain a new scaling function is dominated by the N→ΔN\to\Delta transition and employing a new scaling variable which is suited to the resonance region. This yields a good representation of the electromagnetic response in both the quasielastic and Δ\Delta regions. The scaling approach is then inverted and predictions are made for charge-changing neutrino reactions at energies of a few GeV, with focus placed on nuclei which are relevant for neutrino oscillation measurements. For this a relativistic treatment of the required weak interaction vector and axial-vector currents for both quasielastic and Δ\Delta-excitation processes is presented.Comment: 42 pages, 9 figures, accepted for publication in Physical Review
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