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Pion electro-production in the Roper region in chiral quark models
Authors: B. Golli, S. Sirca, M. Fiolhais
Ref.: The European Physical Journal A - Hadrons and Nuclei 42, 185-193 (2009)
Abstract: 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 M1− and the S1− amplitudes in the P11 partial wave in a simple chiral quark model. A good agreement with the observed M1− amplitude is found with a significant contribution from the pion cloud. The same effect is also prominent in the S1− amplitude but a rather uncertain data prevent us to draw a definitive conclusion.
