2005/12/31 by Vladimir Pascalutsa, Marc Vanderhaeghen · 3 citations
Physics and Astronomy · #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #hep-ph #nucl-th
paper · pdf · doi:10.1103/physrevd.73.034003
published as Phys.Rev.D73:034003,2006 · 38 pages, 14 figures; version to be published in Phys. Rev. D
arxiv created 2006/01/19 · openalex publication_date 2006/02/07 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We develop an extension of chiral perturbation theory to the \ensuremathΔ(1232)-resonance energy region and apply it to investigate the pion electroproduction off the nucleon (e^\ensuremath-N\ensuremath→e^\ensuremath-N\ensuremathπ). We present a complete calculation of this process, in the \ensuremathΔ-resonance region, up to next-to-leading order in the \ensuremathδ expansion. At this order, the only free parameters are the three low-energy constants corresponding to the magnetic (M1), electric (E2), and Coulomb (C2) \ensuremathγN\ensuremath→\ensuremathΔ transition strength. After fitting these parameters to a few well-known data, our calculation provides a prediction for observables and multipole amplitudes of pion electroproduction. These results compare favorably with the phenomenological multipole solutions and recent experimental results from MIT-Bates and MAMI. Our prediction for the pion-mass dependence of the \ensuremathγN\ensuremathΔ form factors offers an explanation for the discrepancy between the recent lattice-QCD results and the experimental value for the ``C2/M1 ratio'' at low Q2.