Chiral effective-field theory in the {delta}(1232) region: Pion electroproduction on the nucleon

Journal Article · Wed Feb 01 04:00:00 EST 2006 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PhysRevD.73.034003· OSTI ID:20776645

Pascalutsa, Vladimir; Vanderhaeghen, Marc ^[1]

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1. 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, Journal Name: Physical Review. D, Particles Fields Journal Issue: 3 Vol. 73; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
AMPLITUDES
CHIRAL SYMMETRY
CHIRALITY
COMPARATIVE EVALUATIONS
DELTA-1232 BARYONS
E2-TRANSITIONS
ELECTRON REACTIONS
ELECTROPRODUCTION
FORM FACTORS
M1-TRANSITIONS
NUCLEONS
PERTURBATION THEORY
PIONS
QUANTUM CHROMODYNAMICS
REST MASS