2,722 research outputs found

    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

    Flutter of asymmetrically swept wings

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    Two formulations of the oblique wing flutter problem are presented; one formulation allows only simple wing bending deformations and rigid body roll as degrees of freedom, while the second formulation includes a more complex bending-torsional deformation together with the roll freedom. Flutter is found to occur in two basic modes. The first mode is associated with wing bending-aircraft roll coupling and occurs at low values of reduced frequency. The second instability mode closely resembles a classical bending-torsion wing flutter event. This latter mode occurs at much higher reduced frequencies than the first. The occurrence of the bending-roll coupling mode is shown to lead to lower flutter speeds while the bending-torsion mode is associated with higher flutter speeds. The ratio of the wing mass moment of inertia in roll to the fuselage roll moment of inertia is found to be a major factor in the determination of which of the two instabilities is critical

    The significance of the integrated Sachs-Wolfe effect revisited

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    We revisit the state of the integrated Sachs-Wolfe (ISW) effect measurements in light of newly available data and address criticisms about the measurements which have recently been raised. We update the data set previously assembled by Giannantonio et al. to include new data releases for both the cosmic microwave background (CMB) and the large-scale structure (LSS) of the Universe. We find that our updated results are consistent with previous measurements. By fitting a single template amplitude, we now obtain a combined significance of the ISW detection at the 4.4 sigma level, which fluctuates by 0.4 sigma when alternative data cuts and analysis assumptions are considered. We also make new tests for systematic contaminations of the data, focusing in particular on the issues raised by Sawangwit et al. Amongst them, we address the rotation test, which aims at checking for possible systematics by correlating pairs of randomly rotated maps. We find results consistent with the expected data covariance, no evidence for enhanced correlation on any preferred axis of rotation, and therefore no indication of any additional systematic contamination. We publicly release the results, the covariance matrix, and the sky maps used to obtain them.Comment: 19 pages, 10 figures. MNRAS in pres
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