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  • Pion electro-production in ...
    Golli, B.; Širca, S.; Fiolhais, M.

    European physical journal. A, Hadrons and nuclei, 11/2009, Volume: 42, Issue: 2
    Journal Article

    We present a method to calculate pion electro-production amplitudes in a coupled-channel framework incorporating quasi-bound quark-model states. The method offers a clear prescription how to extract the resonant part of the amplitudes, even in the presence of different decay channels and a strong mixing of neighbouring resonances. The method is applied to the calculation of the M 1- and the S 1- amplitudes in the P 11 partial wave in a simple chiral quark model. A good agreement with the observed M 1- amplitude is found with a significant contribution from the pion cloud. The same effect is also prominent in the S 1- amplitude but a rather uncertain data prevent us to draw a definitive conclusion.