48 research outputs found

    Numerical Study of Gluon Propagator and Confinement Scenario in Minimal Coulomb Gauge

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    We present numerical results in SU(2) lattice gauge theory for the space-space and time-time components of the gluon propagator at equal time in the minimal Coulomb gauge. It is found that the equal-time would-be physical 3-dimensionally transverse gluon propagator Dtr(k)D^{tr}(\vec{k}) vanishes at k=0\vec{k} = 0 when extrapolated to infinite lattice volume, whereas the instantaneous color-Coulomb potential D44(k)D_{44}(\vec{k}) is strongly enhanced at k=0\vec{k} = 0. This has a natural interpretation in a confinement scenario in which the would-be physical gluons leave the physical spectrum while the long-range Coulomb force confines color. Gribov's formula Dtr(k)=(k/2)[(k2)2+M4]1/2D^{tr}(\vec{k}) = (|\vec{k}|/2)[(\vec{k}^2)^2 + M^4]^{1/2} provides an excellent fit to our data for the 3-dimensionally transverse equal-time gluon propagator Dtr(k)D^{tr}(\vec{k}) for relevant values of k\vec{k}.Comment: 23 pages, 12 figures, TeX file. Minor modifications, incorporating referee's suggestion

    K* nucleon hyperon form factors and nucleon strangeness

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    A crucial input for recent meson hyperon cloud model estimates of the nucleon matrix element of the strangeness current are the nucleon-hyperon-K* (NYK*) form factors which regularize some of the arising loops. Prompted by new and forthcoming information on these form factors from hyperon-nucleon potential models, we analyze the dependence of the loop model results for the strange-quark observables on the NYK* form factors and couplings. We find, in particular, that the now generally favored soft N-Lambda-K* form factors can reduce the magnitude of the K* contributions in such models by more than an order of magnitude, compared to previous results with hard form factors. We also discuss some general implications of our results for hadronic loop models.Comment: 9 pages, 8 figures, new co-author, discussion extended to the momentum dependence of the strange vector form factor

    The Physics of the B Factories

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    Passive Q-switching and mode-locking for the generation of nanosecond to femtosecond pulses

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    Flavor symmetry breaking in quark magnetic moments

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    We discuss the magnetic moments of the baryons allowing for flavor symmetry breaking in the quark magnetic moments. We show that there is a correlation between isospin symmetry breaking and data for the nucleon spin structure obtained from deep inelastic scattering. For small values of the isospin symmetry breaking, of the order of 5%5\%, the magnetic moments and weak axial-vector form factors alone indicate a value of the spin polarization ΔΣ0.20\Delta\Sigma \leq 0.20. Larger values of the spin polarization are compatible only with large isospin symmetry breaking. We also calculate weak axial-vector form factors, which are independent of the symmetry breakings, from magnetic moment data and find good agreement with experiment.Comment: 11 pages, REVTeX, TRITA-TFY-93-08 1 figure has been added (available via conventional mail), some parts has been rewritte
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