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Beam-helicity asymmetry in photon and pion electroproduction in the $\Delta$(1232) resonance region at $Q^2$= 0.35 $(GeV/c)^2$

Abstract : The beam-helicity asymmetry has been measured simultaneously for the reactions (e p \to e p \gamma) and (e p \to e p \pi^0) in the $\Delta (1232)$ resonance region at $Q^2=$ 0.35 (GeV/c)$^2$. The experiment was performed at MAMI with a longitudinally polarized beam and an out-of-plane detection of the proton. The results are compared with calculations based on Dispersion Relations for virtual Compton scattering and with the MAID model for pion electroproduction. There is an overall good agreement between experiment and theoretical calculations. The remaining discrepancies may be ascribed to an imperfect parametrization of some $\gamma^{(*)} N \to \pi N$ multipoles, mainly contributing to the non-resonant background. The beam-helicity asymmetry in both channels ($\gamma$ and $\pi^0$) shows a good sensitivity to these multipoles and should allow future improvement in their parametrization.
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http://hal.in2p3.fr/in2p3-00121621
Contributor : Jeanine Pellet <>
Submitted on : Thursday, December 21, 2006 - 2:18:53 PM
Last modification on : Thursday, May 9, 2019 - 3:50:02 PM

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I.K. Bensafa, P. Achenbach, M. Ases Antelo, C. Ayerbe, D. Baumann, et al.. Beam-helicity asymmetry in photon and pion electroproduction in the $\Delta$(1232) resonance region at $Q^2$= 0.35 $(GeV/c)^2$. European Physical Journal A, EDP Sciences, 2007, 32, pp.69-75. ⟨10.1140/epja/i2006-10277-3⟩. ⟨in2p3-00121621⟩

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