Chiral Effective-Field Theory in the $$\Delta$$(1232) Region: I. Pion Electroproduction on the Nucleon

Journal Article · Fri Jan 20 04:00:00 EST 2006

OSTI ID:862406

Pascalutsa, Vladimir; Vanderhaeghen, Marc

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}.

• Research Organization: Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA
• Sponsoring Organization: USDOE - Office of Energy Research (ER)
• DOE Contract Number: AC05-84ER40150
• OSTI ID: 862406
• Report Number(s): JLAB-THY-06-458; DOE/ER/40150-3672
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
AMPLITUDES
ELECTROPRODUCTION
FORECASTING
FORM FACTORS
MULTIPOLES
NUCLEONS
PERTURBATION THEORY
PIONS