8,935 research outputs found

    Direct J/psi and psi' Polarization and Cross Sections at the Tevatron

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    Transverse polarization of 3S1{}^3 S_1 charmonium states, produced directly in ppˉp\bar{p} collisions at asymptotically large transverse momentum p_t, has emerged as the most prominent test of color octet contributions and spin symmetry in quarkonium production. We present predictions for the polar angle distribution at moderate values of p_t \sim 4 - 20 GeV, covered by the Tevatron Run I data. We update the fits of NRQCD matrix elements and discuss their theoretical uncertainties. With our best fit values, no transverse polarization is expected at p_t \sim 5 GeV, but the angular distribution is predicted to change dramatically as p_t increases to 20 GeV.Comment: 11 pages, LaTeX, 3 figures included via epsf.st

    SUSY Particle Production at the Tevatron

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    The calculation of the next-to-leading order SUSY-QCD corrections to the production of squarks, gluinos and gauginos at the Tevatron is reviewed. The NLO corrections stabilize the theoretical predictions of the various production cross sections significantly and lead to sizeable enhancements of the most relevant cross sections for scales near the average mass of the produced massive particles. We discuss the phenomenological consequences of the results on present and future experimental analyses.Comment: 13 pages, latex, 9 figures, further extended versio

    Observations of Outflowing UV Absorbers in NGC 4051 with the Cosmic Origins Spectrograph

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    We present new Hubble Space Telescope (HST)/Cosmic Origins Spectrograph observations of the Narrow-Line Seyfert 1 galaxy NGC 4051. These data were obtained as part of a coordinated observing program including X-ray observations with the Chandra/High Energy Transmission Grating (HETG) Spectrometer and Suzaku. We detected nine kinematic components of UV absorption, which were previously identified using the HST/Space Telescope Imaging Spectrograph. None of the absorption components showed evidence for changes in column density or profile within the \sim 10 yr between the STIS and COS observations, which we interpret as evidence of 1) saturation, for the stronger components, or 2) very low densities, i.e., n_H < 1 cm^-3, for the weaker components. After applying a +200 km s^-1 offset to the HETG spectrum, we found that the radial velocities of the UV absorbers lay within the O VII profile. Based on photoionization models, we suggest that, while UV components 2, 5 and 7 produce significant O VII absorption, the bulk of the X-ray absorption detected in the HETG analysis occurs in more highly ionized gas. Moreover, the mass loss rate is dominated by high ionization gas which lacks a significant UV footprint.Comment: 41 pages, 10 Figures; accepted for publication in the Astrophysical Journa

    Mollusca of the Illinois River, Arkansas

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    The Illinois River is in the Ozark region of northwestern Arkansas and eastern Oklahoma. A survey of the Illinois River in Arkansas produced nine species and one morphological subspecies of gastropods, three species of sphaeriid clams, and 23 species of unionid mussels. Museum records resulted in another two species and an ecophenotype of the Unionidae. This represents the first published survey of molluscan species from the Illinois River in Arkansas
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