Compton Scattering by the Proton using a Large-Acceptance Arrangement
摘要
Compton scattering by the proton has been measured using the tagged-photon facility at MAMI (Mainz) and the large-acceptance arrangement LARA. The new data are interpreted in terms of dispersion theory based on the SAID-SM99K parameterization of photo-meson amplitudes. It is found that two-pion exchange in the t-channel is needed for a description of the data in the second resonance region. The data are well represented if this channel is modeled by a single pole with mass parameter m(sigma)=600 MeV. The asymptotic part of the spin dependent amplitude is found to be well represented by pi-0-exchange in the t-channel. A backward spin-polarizability of gamma(pi)=(-37.1+-0.6(stat+syst)+-3.0(model))x10^{-4}fm^4 has been determined from data of the first resonance region below 455 MeV. This value is in a good agreement with predictions of dispersion relations and chiral pertubation theory. From a subset of data between 280 and 360 MeV the resonance pion-photoproduction amplitudes were evaluated leading to a E2/M1 multipole ratio of the p-to-Delta radiative transition of EMR(340 MeV)=(-1.7+-0.4(stat+syst)+-0.2(model))%. It was found that this number is dependent on the parameterization of photo-meson amplitudes. With the MAID2K parameterization an E2/M1 multipole ratio of EMR(340 MeV)=(-2.0+-0.4(stat+syst)+-0.2(model))% is obtained.
引用
@article{arxiv.nucl-ex/0109013,
title = {Compton Scattering by the Proton using a Large-Acceptance Arrangement},
author = {S. Wolf and V. Lisin and R. Kondratiev and A. M. Massone and G. Galler and J. Ahrens and H. -J. Arends and R. Beck and M. Camen and G. P. Capitani and P. Grabmayr and F. Härter and T. Hehl and P. Jennewein and K. Kossert and A. I. L'vov and C. Molinari and P. Ottonello and R. O. Owens and J. Peise and I. Preobrajenskij and S. Proff and A. Robbiano and M. Sanzone and M. Schumacher and M. Schmitz and F. Wissmann},
journal= {arXiv preprint arXiv:nucl-ex/0109013},
year = {2013}
}