We report the first extraction of the pion-nucleon multipoles near the production threshold for the + channel at relatively high momentum transfer (Q2 up to 4.2 GeV2). The dominance of the s-wave transverse multipole (E0+), expected in this region, allowed us to access the generalized form factor G1 within the light-cone sum-rule (LCSR) framework as well as the axial form factor GA. The data analyzed in this work were collected by the nearly 4π CEBAF Large Acceptance Spectrometer (CLAS) using a 5.754-GeV electron beam on a proton target. The differential cross section and the π-N multipole E0+/GD were measured using two different methods, the LCSR and a direct multipole fit. The results from the two methods are found to be consistent and almost Q2 independent.

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Copyright © 2012 American Physical Society. This article first appeared in Physical Review C 85, no. 3 (March 2012): 035208-1-35208-15. doi:10.1103/PhysRevC.85.035208.

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