1. Beam-helicity asymmetry in photon and pion electroproduction in the Δ(1232)-resonance region at Q2 = 0.35(GeV/c)2
- Author
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Bensafa, I.K., Achenbach, P., Ases Antelo, M., Ayerbe, C., Baumann, D., Böhm, R., Bosnar, Damir, Burtin, E., Defaÿ, D'Hose, N., Ding, M., Distler, M.O., Doria, L., Fonvieille, H., Friedrich, J.M., Friedrich, J., Garcia Llongo, J., Janssens, P., Jover Manas, G., Kohl, M., Laveissiere, G., Lloyd, M., Makek, Mihael, Marroncle, J., Merkel, H., Merle, P., Müller, U., Nungesser, L., Pasquini, B., Perez Benito, R., Pochodzalla, J., Potokar, M., Rosner, G., Sanchez Majos, S., Seimetz, M., Sirca, S., Spitzenberg, T., Tamas, G., Van de Vyver, R., Van Hoorebeke, L., Walcher, Th., Weis M., Laboratoire de Physique Corpusculaire - Clermont-Ferrand (LPC), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée (DAPNIA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), and MAMI-A1
- Subjects
Nuclear and High Energy Physics ,Particle physics ,Photon ,Proton ,media_common.quotation_subject ,FOS: Physical sciences ,[PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex] ,01 natural sciences ,7. Clean energy ,Asymmetry ,Resonance (particle physics) ,High Energy Physics - Experiment ,High Energy Physics - Experiment (hep-ex) ,High Energy Physics - Phenomenology (hep-ph) ,Pion ,Dispersion relation ,0103 physical sciences ,[PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex] ,Nuclear Experiment ,010306 general physics ,media_common ,Physics ,010308 nuclear & particles physics ,Compton scattering ,Helicity ,High Energy Physics - Phenomenology ,[PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph] ,Electromagnetic processes and properties ,Elastic and Compton scattering ,Meson production ,Baryon resonances - 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., Comment: 7 pages, 8 figures, version to appear in EPJA
- Published
- 2007