A nonrelativistic operator for pion electroproduction

Dressler, Edward T.

doi:10.1139/p88-042

Cited by 11 publications

(2 citation statements)

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“…Even though the cause of this problem can be understood and addressed when one consistently deals with the origin of the internal structure, most authors reverted to a variety of ad hoc recipes to restore gauge invariance in Born-type amplitudes: terms are added by hand or form factors are adjusted to yield a conserved current. In pion electroproduction, for example, a commonly made assumption for this purpose is that the pion and nucleon isovector form factors are identical [8][9][10]. Similary, both the pion-pole term and the nucleon-pole term, which is needed for gauge invariance, are proportional to the pion form factor in the model [11,12] used to analyze the data in Ref.…”

Section: Introductionmentioning

confidence: 99%

Hadron structure in the description of electromagnetic reactions

2002

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Hadron structure in the description of electromagnetic reactions Koch, J.; Pascalutsa, V.V.; Scherer, S. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. The description of electromagnetic reactions at intermediate energies, such as pion electroproduction or ͑virtual͒ Compton scattering, traditionally starts from covariant tree-level Feynman diagrams ͑Born or pole terms͒. Internal hadron structure is included by means of ͑on-shell͒ form factors in the vertices while free propagators are used. To overcome problems with gauge invariance, simple prescriptions, such as, choosing F 1 V (q 2 )ϭF (q 2 ) in pion electroproduction or the ''minimal substitution,'' are used. We discuss the inherent assumptions of such approaches and study the general structure of electromagnetic vertices and propagators for pions and nucleons. We show which part of the vertex is entirely determined through the Ward-Takahashi identity and point out that detailed features of the q 2 dependence of the form factors cannot be derived from this condition. Recipes to enforce gauge invariance, including the minimal substitution, are critically examined in the light of the exact treatment. The interplay between irreducible contact terms and ''off-shell effects'' in vertices and propagators is demonstrated for real Compton scattering on a pion. The need for a consistent microscopic treatment of reaction amplitudes is stressed and illustrated by an example in the framework of chiral perturbation theory. Shortcomings of the minimal substitution method when applied to effective Lagrangians are pointed out.

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Section: Introductionmentioning

confidence: 99%

Hadron structure in the description of electromagnetic reactions

2002

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“…Events are generated by convoluting an elementary process on a nucleon or a quasi-deuteron with the Fermi motion of the interacting system within the "C nucleus. As elementary cross sections we use the Rosenbluth formula for 'H(e, e'p) and the Dressler formalism [38] for pion production. The (e, e' p)n cross section is estimated from the ( y, pn) photo-dissociation strength as parametrized by Rossi et al [39].…”

Section: Monte Carlo Simulationmentioning

confidence: 99%

The 12C(e, e′p) and 12C(e, e′pp) reactions in the Δ-resonance region

et al. 1995

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Link to publication Citation for published version (APA):Zondervan, A., de Bever, L. J., Jans, E., Konijn, J., Kruijer, M., Steijger, J. J. M., ... Vanderhaeghen, M. (1995). The 12C(e, ep) and 12C(e, epp) reactions in the -resonance region. Nuclear Physics A, 587(4), 697-720. DOI: 10.1016/0375-9474(95)00044-2 General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. The 12C(e, e' p) and 12C(e, e' pp) reactions in the A-resonance region AbstractCoincidence cross sections for the "C(e, e'pp) and "C(e, e'p) reactions have been measured in the A-resonance region. The '*C(e, e'pp) reaction has been measured at three different angular settings of the proton detectors to investigate the angular correlation between the emitted protons. The data, which have a low statistical accuracy, are compared with a calculation based on the direct-knockout mechanism, which includes one-and two-body currents. NN-correlations are accounted for via a correlation function, A-excitation via a two-body current and final-state interactions of the emitted protons via an optical potential. The "C(e, e'p) data, taken at large proton-emission angles, cover the region of high missing-energy values

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Pion-production experiments at NIKHEF

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Chiral Dynamics: Theory and Experiment

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A nonrelativistic operator for pion electroproduction

Cited by 11 publications

References 2 publications

Hadron structure in the description of electromagnetic reactions

Hadron structure in the description of electromagnetic reactions

The 12C(e, e′p) and 12C(e, e′pp) reactions in the Δ-resonance region

Pion-production experiments at NIKHEF

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