https://doi.org/10.1140/epja/i2009-10878-2
Regular Article - Theoretical Physics
Pion electro-production in the Roper region in chiral quark models
1
Faculty of Education, University of Ljubljana and J. Stefan Institute, 1000, Ljubljana, Slovenia
2
Faculty of Mathematics and Physics, University of Ljubljana and J. Stefan Institute, 1000, Ljubljana, Slovenia
3
Department of Physics and Centre for Computational Physics, University of Coimbra, 3004-516, Coimbra, Portugal
* e-mail: bojan.golli@ijs.si
Received:
11
June
2009
Revised:
8
September
2009
Accepted:
17
September
2009
Published online:
3
October
2009
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.
PACS: 11.80.Gw Multichannel scattering – / 12.39.Ba Bag model – / 13.60.Le Meson production – / 14.20.Gk Baryon resonances with S = 0 –
© SIF, Springer-Verlag Berlin Heidelberg, 2009