A coherent state of pions is introduced to the nonrelativistic quark model. The coherent pair approximation is employed for the pion field in order to maintain the spin-isospin symmetry. In this approximation the pion is localized in the momentum space, and the vertex form factor in the pion-quark interaction is derived from this localization. The nucleon masses and wave functions are calculated using this model, and our results are compared to those of the quark model with the one pion exchange potential. Similar result is obtained for the mass spectrum, but there exists a clear difference in the internal structure of nucleon resonances.

The N * (1440) → Nππ decay is studied by making use of the chiral reduction formula. This formula suggests a scalar-isoscalar pion-baryon contact interaction that is absent in the recent study of Hernández et al. [Phys. Rev. C 66, 065201 (2002)]. The contact interaction is introduced into their model and is found to be necessary for the simultaneous description of g RNππ and the ππ and πN invariant mass distributions.