2004/11/03 by T. Sato, Toshiro Sato, T. -S. H. Lee +5
Physics and Astronomy · #FOS: Physical sciences #High-Energy Particle Collisions Research #Nuclear Theory (nucl-th) #Nuclear physics research studies #Quantum Chromodynamics and Particle Interactions #nucl-th
paper · pdf · doi:10.48550/arxiv.nucl-th/0411013
26 pages, 13 figures
arxiv created 2004/11/03 · openalex publication_date 2004/11/03 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
By applying a unitary transformation method, we have derived the leading-order corrections on the effective Hamiltonian of a dynamical model developed in Phys. Rev. C54, 2660 (1996) for electromagnetic pion production reactions. The resulting energy-independent one-loop corrections on the baryon masses and the gamma N -> Delta vertex interaction are associated with the structure of the nucleon and Delta and have been calculated within a constituent quark model. We find that the one-loop corrections on the magnetic M1 transition of the gamma N -> Delta are very small, while their contributions to the electric E2 and Coulomb C2 transitions are found to be in opposite signs of that due to pion cloud effects associated with the scattering states. Our results further indicate that the determination of the nonspherical L=2 components of the constituent quark wavefunctions of N and Delta from the extracted empirical E2 and C2 form factors requires a rigorous and complete calculation of meson cloud effects. We also find that the one-loop corrections on the non-resonant pion production operator can resolve the difficulty in describing the near threshold gamma p -> pi0 p reaction. Possible future developments are discussed.