1,201 research outputs found

    \cN = 1 supersymmetric constraints for evolution kernels

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    We provide a complete set of supersymmetric constraints for the anomalous dimensions of the conformal twist-two operators to all orders of perturbation theory. Employing them we derive new relations between the exclusive evolution kernels and apply them in QCD in order to get definite predictions at leading order and beyond.Comment: LaTeX, npb.sty required, 4 pages, Talk given at the 7th International Workshop on Deep Inelastic Scattring and QCD, DESY-Zeuthen, April 19-23, 199

    Global analysis of helicity PDFs: past - present - future

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    We discuss the current status of the DSSV global analysis of helicity-dependent parton densities. A comparison with recent semi-inclusive DIS data from COMPASS is presented, and constraints on the polarized strangeness density are examined in some detail.Comment: Talk presented at the XIX Int. Workshop on Deep-Inelastic Scattering and Related Subjects (DIS 2011); 4 pages; 2 figure

    Polarized semi-inclusive electroweak structure functions at next-to-leading-order

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    We present a next-to-leading order (NLO) computation of the full set of polarized and unpolarized electroweak semi-inclusive DIS (SIDIS) structure functions, whose knowledge is crucial for a precise extraction of polarized parton distributions. We focus on the phenomenology of the polarized structure functions for the kinematical conditions that could be reached in an Electron-Ion-Collider. We show that the NLO corrections are sizeable, particularly in the small-xx range. We test the sensitivity of these structure functions on certain quark distributions and compare it to the situation of inclusive DIS and electromagnetic SIDIS.Comment: 17 pages, 5 figure

    Off-forward gluonometry

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    We explore the deeply virtual Compton scattering process at NLO with the emphasis on the measurement of the tensor gluon skewed distributions. We recalculate the one-loop coefficient function and give two-loop results for anomalous dimensions and exclusive evolution kernels required for studying the logarithmic scaling violation. We evaluate weighted cross sections which give direct access to these functions on experiment.Comment: 11 pages, LaTeX, 3 figure

    QCD resummation in hadron production

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    We present calculations of next-to-leading order and resummed QCD corrections for semi-inclusive deep-inelastic scattering and single-inclusive e+e− annihilation. The resummation is performed to next-to-leading logarithmic accuracy. Knowing these QCD corrections is important in order to extract parton distribution functions and fragmentation functions from present and future data for these reactions. We present phenomenological results relevant for the COMPASS, HERMES, and BELLE experiments

    Mycorrhizal densities decline in association with nonnative plants and contribute to plant invasion

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    Belowground interactions between herbaceous native species and nonnative species is a poorly understood but emerging area of interest to invasive-species researchers. Positive feedback dynamics are commonly observed in many invaded systems and have been suspected in California grasslands, where native plants associate strongly with soil mutualists such as arbuscular mycorrhizal fungi. In response to disturbance, invading nonnative plants proliferate, and to the degree these species associate weakly with soil mutualists, we would expect mutualist efficacy to degrade over time. Degraded mutualist efficacy would negatively impact mutualist-dependent native species or their recruitment following a disturbance. We investigated the feedback dynamics of soil conditioned both with native and nonnative herbaceous communities of southern California grasslands to test this degraded mutualist hypothesis. Using a mesocosm approach, we inoculated each community with live soil originating from a remnant native grassland and varied the plant communities (i.e., native or nonnative) along a plant–species-richness gradient. After one year, we then used this conditioned soil for reciprocal feedback tests on a native and nonnative indicator species. We show that a native herbaceous forb (Gnaphalium californicum) grows best in soil conditioned by a diverse mix of other native species that includes G. californicum but is inhibited by soil conditioned by a diverse mix of nonnative species. We also show that an invasive, nonnative herbaceous forb (Carduus pycnocephalus) exhibits strong growth in soil lacking arbuscular mycorrhizal fungi and in soil conditioned by a diverse mix of nonnative species that include C. pycnocephalus, and that it is inhibited by the same soil that best promotes the native, G. californicum. Separate bioassays for mycorrhizal density show a reduction of arbuscular mycorrhizal fungi in the nonnative-conditioned soil relative to the native-conditioned soil, which suggests that nonnative species do not promote the growth of mycorrhizal fungi in the same way that native species do. The growth patterns resulting from the vegetative history of these distinct soil communities provide evidence of a biotic feedback mechanism that may account for the maintenance of persistent communities of nonnative (and often invasive) plants ubiquitous throughout California grasslands

    The Transformational Effects of Public-Private Partnerships in Cleveland: An Inside View of Good Government under Mayors Voinovich and Jackson

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    This article focuses on two mayoral-led public-private partnerships designed to renew good government in Cleveland — Mayor George Voinovich’s Operations Improvement Task Force (OITF) (1979-1982) and Mayor Frank Jackson’s Operations Efficiency Task Force (OETF) (2006-2009). The Voinovich OITF public-private partnership enabled Cleveland to “come back” after the city’s 1978 default. The Jackson OETF public-private partnership successfully rightsized Cleveland in relationship to its much smaller population needs during challenging economic times without disruptions in service. The authors use three data sources, including interviews with both mayors and their key partnership managers, to gain a complete inside picture of each mayoral-led public-private partnership. The article concludes with the lessons learned and the governance implications of a mayoral-led public-private partnership in fostering long-term (transformative) administrative change. This article shows how both mayoral-led public-private partnerships quietly transformed Cleveland’s government to meet the demands of fewer resources, greater complexity, more transparency, and more timely decisions in the delivery of public services to citizens
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