Chiral Perturbation Theory, Large-N_c and the eta' Mass

Abstract

Using chiral perturbation theory and the large-$N_c$ expansion, we obtain expressions for the ${\eta }^{\prime }$ mass and $\eta -{\eta }^{\prime }$ mixing in terms of low-energy chiral Lagrangian parameters. This is accomplished through an intermediate step of `matching' the topological susceptibility in the large-$N_c$ and chiral Lagrangian descriptions. By inserting the values of well-measured parameters we obtain predictions involving the the second order parameters $L_6,L_7$ and $L_8$. The prediction for $L_6$ is quite restrictive even after allowing for $1/N_c$ corrections.

Comments: 11 pages, Latex, 3 figures using epsf