Dispersion relation analysis of neutral pion photo- and electroproduction at threshold using the MAID and SAID solutions

Abstract

Neutral pion photo- and electroproduction at threshold is analyzed in the framework of dispersion relations. For this purpose, we evaluate the real threshold amplitudes in terms of Born contributions and dispersion integrals determined by the imaginary parts of the MAID and SAID multipoles. The results show considerable cancellations between Born terms and resonance contributions. Good agreement with the data is found for photoproduction. While our dispersion analysis suggests considerable discrepancies for electroproduction, the present state of the experimental multipole analysis at finite Q^2 does not permit drawing conclusions at this time.

arXiv comment22 pages LATEX including 4 postscript figures

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Cited by in corpus (8)

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• P-wave excited baryons from pion- and photo-induced hyperon production
• Dispersion Theory and the Low Energy Constants for Neutral Pion Photoproduction
• Fixed-t analyticity as a constraint in single energy partial wave analyses of meson photoproduction reactions
• A precision measurement of the $p$($e,e^{\prime }p$)${\pi }^0$ reaction at threshold
• Irreducible tensor approach to spin observables in photo production of mesons with arbitrary spin-parity $s^{\pi }$