20 research outputs found

    Deeply Virtual Compton Scattering at Jefferson Lab, Results and Prospects

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    Recent results from the Deeply Virtual Compton Scattering (DVCS) program at Jefferson Lab will be presented. Approved dedicated DVCS experiments at 6 GeV and plans for the 12 GeV upgrade will be discussed.Comment: 6 pages and and 6 figures Subj-clas

    Deeply Virtual Compton Scattering with CLAS12

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    An overview is given about the capabilities provided by the JLab 12 GeV Upgrade to measure deeply virtual exclusive processes with high statistics and covering a large kinematics range in the parameters that are needed to allow reconstruction of a spatial image of the nucleon's quark structure. The measurements planned with CLAS12 will cross section asymmetries with polarized beams and with longitudinally and transversely polarized proton targets in the constrained kinematics x=±ξx = \pm \xi. In addition, unpolarized DVCS cross sections, and doubly polarized beam target asymmetries will be measured as well. In this talk only the beam and target asymmetries will be discussed.Comment: 6 pages, 3 figures, talk presented at the Workshop on Deeply Exclusive Processes, Jefferson Lab, 200

    New measurement of charge asymmetry xF3x{F}_3 from HERA

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    After presenting the recent measurements of neutral current cross section in DIS at HERA, we explain the effect of the γ−Z0\gamma-Z_0 interference at the electro-weak scale, visible on these data. Then, the beam charge difference xF3x{F}_3 is measured and the interference itself is extracted. Results are discussed in the context of perturbative QCD.Comment: 4 pages, 3 figures, proceedings of the International Workshop on Positrons at Jefferson Lab (March 25-27, 2009), Thomas Jefferson National Accelerator Facility, Newport News, V

    Two-photon exchange measurements with positrons and electrons

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    Two-photon exchange contributions have potentially broad ranging impact on several charged lepton scattering measurements. Previously believed to be extremely small, based in part on comparisons of positron scattering and electron scattering in the 1950s and 1960s, recent data suggest that the corrections may be larger than expected, in particular in kinematic regions that were inaccessible in these early positron scattering measurements. Additional measurements using positron beams at Jefferson Lab would allow for a detailed investigation of these contributions in a range of reactions and observables.Comment: 6 pages, proceedings from the International Workshop on Positrons at Jefferson Lab (JPOS09), Jefferson Lab, Newport News, VA, March 25-27, 200

    GPDs and DVCS with Positrons

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    The beam charge asymmetry helps to isolate the real part of the deeply virtual Compton scattering (DVCS) amplitude. It is discussed what information can be gained both from the real and imaginary part of the DVCS amplitude.Comment: 5 pages, 2 figures, invited talk at `Workshop on Positrons at Jefferson Lab

    A new highly segmented start counter for the CLAS detector

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    The design, construction and performance of a highly segmented Start Counter are described. The Start Counter is an integral part of the trigger used in photon beam running with CLAS in Hall B at the Thomas Jefferson National Accelerator Facility (TJNAF). The Start Counter is constructed of 24 2.2-mm-thick single-ended scintillation paddles, forming a hermetic hexagon around the target region. This device measures the interaction time of the incoming photon in the target by detecting the outgoing particles. The counter provides complex trigger topologies, shows good efficiency and achieved a time resolution of 350 ps

    Etude experimentale de l'electroproduction du #PI#"+ sur le proton du seuil: contribution a la mesure du facteur de forme axial du nucleon

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    SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 79478 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc