777 research outputs found

    Measuring Vacuum Polarization with Josephson Junctions

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    We argue that the vacuum polarization by the virtual electron-positron pairs can be measured by studying a Josephson junction in a strong magnetic field. The vacuum polarization results in a weak dependence of the Josephson constant on the magnetic field strength which is within the reach of the existing experimental techniques.Comment: 4 pages, 2 figures, LaTe

    Coulomb Artifacts and Breakdown of Perturbative Matching in Lattice NRQCD

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    By studying an explicit analytical solution of the Coulomb problem on the lattice we demonstrate a breakdown of perturbative matching for the description of the Coulomb artifacts in lattice NRQCD, which leads to a large systematic error in the predictions for the heavy quarkonium spectrum. The breakdown is a result of a fine interplay between the short and long distance effects specific to the lattice regularization of NRQCD. We show how the problem can be solved within the Schrodinger matching procedure.Comment: 11 pages, 1 figure. Journal version (minor revisions implemented

    Ultrasoft Effects in Heavy-Quarkonium Physics

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    In the framework of nonrelativistic QCD, we consider a new class of radiative corrections, which are generated at next-to-next-to-next-to-leading order through the chromoelectric dipole interaction of heavy quarkonium with ultrasoft virtual gluons. We provide analytical formulae from which the resulting shifts in the quarkonium energy levels and the wave functions at the origin may be calculated. We discuss the phenomenological implications for the top-antitop and Upsilon systems and point out some limitations of describing charmonium using a Coulomb potential.Comment: 14 pages (Latex), 5 figures (Axodraw), one reference added, accepted for publication in Nuclear Physics

    Bottom Quark Mass from Υ\Upsilon Sum Rules to O(αs3){\cal O}(\alpha_s^3)

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    We use the O(αs3){\cal O}(\alpha_s^3) approximation of the heavy-quark vacuum polarization function in the threshold region to determine the bottom quark mass from nonrelativistic Υ\Upsilon sum rules. We find very good stability and convergence of the perturbative series for the bottom quark mass in MS\rm\overline{MS} renormalization scheme. Our final result is mb(mb)=4.169±0.008th±0.002αs±0.002exp\overline{m}_b(\overline{m}_b)=4.169\pm 0.008_{th}\pm 0.002_{\alpha_s}\pm 0.002_{exp}.Comment: 23 pages, 6 figures, journal versio