A unitary isobar model for pion photo- and electroproduction on the proton up to 1 GeV |
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| Institution: | 1. AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, 30-059 Kraków, Poland;2. RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, NY 11973, USA;3. Department of Physics, Western Michigan University, Kalamazoo, MI 49008, USA;1. Faculty of Physics, Baku State University, AZ-1148, Baku, Azerbaijan;2. Physics Department, Middle East Technical University, 06531 Ankara, Turkey;1. Institute of Mechatronic Systems, Zurich University of Applied Sciences, Technikumstrasse 5, CH-8401 Winterthur, Switzerland;2. Physik-Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland;1. Department of Physics and Institute of Theoretical Physics, Nanjing Normal University, Nanjing, Jiangsu 210023, PR China;2. School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou 221116, PR China;3. Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems, Nanjing Normal University, Nanjing, Jiangsu 210023, PR China;1. Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan;2. Department of Physics, Hokkaido University, Sapporo 060-0810, Japan;3. Department of Physics, Chung-Yuan Christian University, 200 Chung-Pei Rd., Chung-Li 320, Taiwan |
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| Abstract: | A new operator for pion photo- and electroproduction has been developed for nuclear applications at photon equivalent energies up to 1 GeV. The model contains Born terms, vector mesons and nucleon resonances (P33(1232), P11(1440), D13(1520), S11(1535), F15(1680), and D33(1700)). The resonance contributions are included taking into account unitarity to provide the correct phases of the pion photoproduction multipoles. The Q2 dependence of electromagnetic resonance vertices is described with appropriate form factors in the electromagnetic helicity amplitudes. Within this model we have obtained good agreement with the experimental data for pion photo- and electroproduction on the nucleon for both differential cross sections and polarization observables. The model can be used as a starting point to predict and analyze forthcoming data. |
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