Abstract
We have measured beam-spin asymmetries to extract the moment from the hard exclusive reaction above the resonance region, for the first time with nearly full coverage from forward to backward angles in the center of mass. The moment has been measured up to in , covering the kinematic regimes of generalized parton distributions (GPD) and baryon-to-meson transition distribution amplitudes (TDA) at the same time. The experimental results in very forward kinematics demonstrate the sensitivity to chiral-odd and chiral-even GPDs. In very backward kinematics where the TDA framework is applicable, we found to be negative, while a sign change was observed near 90° in the center of mass. The unique results presented in this Letter will provide critical constraints to establish reaction mechanisms that can help to further develop the GPD and TDA frameworks.
- Received 27 March 2020
- Revised 8 June 2020
- Accepted 30 July 2020
DOI:https://doi.org/10.1103/PhysRevLett.125.182001
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