Chiral effective-field theory in the {delta}(1232) region: Pion electroproduction on the nucleon
- Physics Department, College of William and Mary, Williamsburg, Virginia 23187 (United States) and Theory Group, Jefferson Lab, 12000 Jefferson Avenue, Newport News, Virginia 23606 (United States)
We develop an extension of chiral perturbation theory to the {delta}(1232)-resonance energy region and apply it to investigate the pion electroproduction off the nucleon (e{sup -}N{yields}e{sup -}N{pi}). We present a complete calculation of this process, in the {delta}-resonance region, up to next-to-leading order in the {delta} expansion. At this order, the only free parameters are the three low-energy constants corresponding to the magnetic (M1), electric (E2), and Coulomb (C2) {gamma}N{yields}{delta} 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 {gamma}N{delta} 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 Q{sup 2}.
- OSTI ID:
- 20776645
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 73, Issue 3; Other Information: DOI: 10.1103/PhysRevD.73.034003; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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