Descripción: A general method is presented for computing matrix elements of quark operators on baryonic states with low strangeness and arbitrary number of colors N c . These results are useful in applications of the large N c expansion to baryons and exotics. As an application we compute the matrix elements of strangeness changing operators contributing to kaon couplings to ground state baryons and pentaquarks, in broken SU (3). © 2006 Elsevier B.V. All rights reserved.

Descripción: We compute the coefficients of the effective mass operator of the 1/N c expansion for negative parity L=1 excited baryons using the Isgur-Karl model in order to compare the general approach, where the coefficients are obtained by fitting to data, with a specific constituent quark model calculation. We discuss the physics behind the fitted coefficients for the scalar part of the most general two-body quark-quark interaction. We find that both pion exchange and gluon exchange lead to the dominance of the same operator at the level of the effective mass operator, which is also observed from data. © 2011 American Institute of Physics.

Descripción: We discuss the matching of the quark model to the effective mass operator of the 1/Nc expansion using the permutation group SN. As an illustration of the general procedure we perform the matching of the Isgur-Karl model for the spectrum of the negative parity L=1 excited baryons. Assuming the most general two-body quark Hamiltonian, we derive two correlations among the masses and mixing angles of these states which should hold in any quark model. These correlations constrain the mixing angles and can be used to test for the presence of three-body quark forces. © 2010 American Institute of Physics.