2007/12/31 by Bruno Juliá-Díaz, B. Julia-Diaz, T. -S. H. Lee +5 · 4 citations
Physics and Astronomy · #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #nucl-th
paper · pdf · doi:10.1103/physrevc.77.045205
published as Phys.Rev.C77:045205,2008 · Corrected version. 14 pages, 10 figures
arxiv created 2008/01/07 · openalex publication_date 2008/04/16 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The electromagnetic pion production reactions are investigated within the dynamical coupled-channels model developed by Matsuyama, Sato, and Lee [Phys. Rep. 439, 193 (2007)]. The meson-baryon channels included in this study are \ensuremathγN,\ensuremathπN,\ensuremathηN, and the \ensuremathπ\ensuremathΔ,\ensuremathρN, and \ensuremathσN resonant components of the \ensuremathπ\ensuremathπN channel. With the hadronic parameters of the model determined in a recent study of \ensuremathπN scattering, we show that the pion photoproduction data up to the second resonance region can be described to a very large extent by only adjusting the bare \ensuremathγN\ensuremath→N* helicity amplitudes, while the nonresonant electromagnetic couplings are taken from previous works. It is found that the coupled-channels effects can contribute about 30--40 % of the production cross sections in the \ensuremathΔ (1232) resonance region, and can drastically change the magnitude and shape of the cross sections in the second resonance region. The importance of the loop-integrations in a dynamical approach is also demonstrated. The meson cloud effects as well as the coupled-channels contributions to the \ensuremathγN\ensuremath→N* form factors are found to be mainly in the low Q2 region. Necessary improvements to the model and future developments are discussed.