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The beam spin asymmetry (BSA) in the exclusive reaction e→p→epπ0 was measured with the CEBAF 5.77 GeV polarized electron beam and Large Acceptance Spectrometer (CLAS). The xB,Q2,t, and ϕ dependences of the π0 BSA are presented in the deep inelastic regime. The asymmetries are fitted with a sinϕ function and their amplitudes are extracted. Overall, they are of the order of 0.04–0.11 and roughly independent of t. This is the signature of a nonzero longitudinal-transverse interference. The implications concerning the applicability of a formalism based on generalized parton distributions, as well as the extension of a Regge formalism at high photon virtualities, are discussed.


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Physical Review C

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R. De Masi et al. [CLAS Collaboration], "Measurement of ep→epπ0 beam spin asymmetries above the resonance region", Physical Review C 77.4 (2008) DOI: 10.1103/PhysRevC.77.042201



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