The Constituent Chiral Quark Model revisited

We reconsider the Constituent Chiral Quark Model of Manohar and Georgi in the presence of SUL(3)×SUR(3) external sources. As recently emphasized by Weinberg, the corresponding effective Lagrangian is renormalizable in the large-Nc limit. We show, however, that the number of the required counterterms depends crucially on the value of gA and it is minimized for gA=1. We then find that with a rather small value for the constituent quark mass, which we fix phenomenologically to MQ=(190±40) MeV, the model reproduces rather well the values of several well-known low-energy constants. We also comment on the limitations of the model as well as on a few exceptional applications, to more complicated low-energy observables, where one can expect the model to make reasonably good predictions.