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From the same journal

Extraction of beam-spin asymmetries from the hard exclusive $π^{+}$ channel off protons in a wide range of kinematics

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  • (CLAS Collaboration)


Publication details

JournalPhysical Review Letters
DateAccepted/In press - 30 Jul 2020
DatePublished (current) - 28 Oct 2020
Number of pages7
Original languageUndefined/Unknown


We have measured beam-spin asymmetries to extract the $\sin\phi$ moment $A_{LU}^{\sin\phi}$ from the hard exclusive $\vec{e} p \to e^\prime n \pi^+$ reaction above the resonance region, for the first time with nearly full coverage from forward to backward angles in the center-of-mass. The $A_{LU}^{\sin\phi}$ moment has been measured up to 6.6 GeV$^{2}$ in $-t$, 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 $A_{LU}^{\sin\phi}$ to be negative, while a sign change was observed near 90$^\circ$ in the center-of-mass. The unique results presented in this paper will provide critical constraints to establish reaction mechanisms that can help to further develop the GPD and TDA frameworks.

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    Research areas

  • nucl-ex, hep-ex, hep-ph

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