Abstract
Differential cross sections of the exclusive process were measured with good precision in the range of the photon virtuality and the invariant mass range of the final state GeV using the Continuous Electron Beam Accelerator Facility Large Acceptance Spectrometer. Data were collected with nearly complete coverage in the azimuthal and polar angles of the center-of-mass system. More than 37 000 cross-section points were measured. The contributions of the isospin resonances , and were extracted at different values of using a single-channel, energy-dependent resonance amplitude analysis. Two different approaches, the unitary isobar model and the fixed- dispersion relations, were employed in the analysis. We observe significant strength of the in the amplitude, which is in strong disagreement with quark models that predict both transverse amplitudes to be strongly suppressed. For the we observe a slow changeover from the dominance of the amplitude at the real photon point to a where begins to dominate. The scalar amplitude drops rapidly with consistent with quark model prediction. For the resonance our analysis shows significant strength for the amplitude at .
15 More- Received 8 December 2014
DOI:https://doi.org/10.1103/PhysRevC.91.045203
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