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Phys. Rev. C 70, 032201(R) (2004) [5 pages]

γ*NΔ form factors from a relativistic dynamical model of pion electroproduction

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G. L. Caia1,*, V. Pascalutsa2,3,†, J. A. Tjon3,4,‡, and L. E. Wright1,§
1Institute of Nuclear and Particle Physics (INPP), Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701, USA
2Department of Physics, The College of William & Mary, Williamsburg, Virginia 23188, USA
3Theory Group, Jefferson Laboratory, 12000 Jefferson Avenue, Newport News, Virginia 23606, USA
4Department of Physics, University of Maryland, College Park, Maryland 20742, USA

Received 28 May 2004; published 9 September 2004

We obtain the electromagnetic form factors of the γNΔ transition by analyzing recent pion-electroproduction data using a fully relativistic dynamical model. Special care is taken to satisfy Ward-Takahashi identities for the Born term in the presence of form factors, thereby allowing the use of realistic electromagnetic form factors of the nucleon and pion. We parametrize the Q2 dependence of the bare γNΔ form factors by a three-parameter form which is consistent with the asymptotic behavior inferred from QCD. The parameters of the bare γNΔ form factors are the only free parameters of the model and are fitted to the differential cross-section and multipole-analysis data up to Q2=4(GeV∕c)2 in the Δ(1232)-resonance region. This analysis emphasizes the significance of the pion-cloud effects in the extraction of the resonance parameters.

© 2004 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevC.70.032201
DOI:
10.1103/PhysRevC.70.032201
PACS:
12.38.Aw, 13.40.Gp, 13.60.Le, 14.20.Gk

*Electronic address: caia@phy.ohiou.edu

†Electronic address: vlad@jlab.org

‡Electronic address: tjon@jlab.org

§Electronic address: wright@ohiou.edu

 
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