Physical Review C
Beam-target double-spin asymmetries and target single-spin asymmetries were measured for the exclusive π+ electroproduction reaction γ∗p→nπ+. The results were obtained from scattering of 6-GeV longitudinally polarized electrons off longitudinally polarized protons using the CEBAF Large Acceptance Spectrometer at Jefferson Laboratory. The kinematic range covered is 1.1 < W < 3 GeV and 1 < Q2 < 6 GeV2. Results were obtained for about 6000 bins in W, Q2, cos(θ∗), and φ∗. Except at forward angles, very large target-spin asymmetries are observed over the entire W region. Reasonable agreement is found with phenomenological fits to previous data for W < 1.6 GeV, but very large differences are seen at higher values of W. A generalized parton distributions (GPD)-based model is in poor agreement with the data. When combined with cross-sectional measurements, the present results provide powerful constraints on nucleon resonance amplitudes at moderate and large values of Q2, for resonances with masses as high as 2.4 GeV. © 2017 American Physical Society.
Original Publication Citation
Bosted, P. E., Amaryan, M. J., Anefalos Pereira, S., Avakian, H., Badui, R. A., Ball, J., . . . Zonta, I. (2017). Target and beam-target spin asymmetries in exclusive pion electroproduction for Q2 > 1 GeV2. I. ep→eπ+n. Physical Review C, 95(3), 035206. doi:10.1103/PhysRevC.95.035206
Posted, P. E.; Amaryan, M. J.; Pereira, S. Anefalos; Avakian, H.; Badui, R. A.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Batourine, V.; Bedlinsky, I.; Bültmann, S.; Kuhn, S. E.; Torayev, B.; Weinstein, L. B.; and Zhang, J., "Target and Beam-Target Spin Asymmetries in Exclusive Pion Electroproduction for Q2 > 1 GeV2 . I. ep → eπ+n" (2017). Physics Faculty Publications. 88.