7,156 research outputs found

    The effect of reionization on the CMB-density correlation

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    In this paper we show how the rescattering of CMB photons after cosmic reionization can give a significant linear contribution to the temperature-matter cross-correlation measurements. These anisotropies, which arise via a late time Doppler effect, are on scales much larger than the typical scale of non-linear effects at reionization; they can contribute to degree scale cross-correlations and could affect the interpretation of similar correlations resulting from the integrated Sachs-Wolfe effect. While expected to be small at low redshifts, these correlations can be large given a probe of the density at high redshift, and so could be a useful probe of the cosmic reionization history.Comment: 8 pages, 8 figure

    Exclusive Production of Neutral Vector Mesons at the Electron-Proton Collider HERA

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    The first five years of operation of the multi-purpose experiments ZEUS and H1 at the electron-proton storage ring facility HERA have opened a new era in the study of vector-meson production in high-energy photon-proton interactions. The high center-of-mass energy available at this unique accelerator complex allows investigations in hitherto unexplored kinematic regions, providing answers to long-standing questions concerning the energy-dependence of the rho, omega, phi, and J/psi production cross sections. The excellent angular acceptance of these detectors, combined with that of specialized tagging detectors at small production angles, has permitted measurements of elastic and inelastic production processes for both quasi-real photons and those of virtuality exceeding the squared mass of the vector meson. This report provides a quantitative picture of the present status of these studies, comparing them to the extensive measurements in this field at lower energies and summarizing topical developments in theoretical work motivated by the new data.Comment: This replacement serves to correct an error in Eq. 3.41. An improved version of this review will appear in book form as Nr. 140 in the series Springer Tracts in Modern Physics on 6.October. 90 pages including 34 figure
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