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Pion Photoproduction Amplitude Relations in the 1/N_c Expansion

Thomas D. Cohen·Daniel C. Dakin·Richard F. Lebed·Daniel R. Martin
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Abstract

We derive expressions for pion photoproduction amplitudes in the 1/N_c expansion of QCD, and obtain linear relations directly from this expansion that relate electromagnetic multipole amplitudes at all energies. The leading-order relations in 1/N_c compare favorably with available data, while the next-to-leading order relations seem to provide only a small improvement. However, when resonance parameters are compared directly, the agreement at O(1/N_c) or O(1/N_c^2) is impressive.

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Thomas D. Cohen, Daniel C. Dakin, Richard F. Lebed, Daniel R. Martin. 2004-12-20. Pion Photoproduction Amplitude Relations in the 1/N_c Expansion. https://doi.org/10.1103/physrevd.71.076010

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