Mixing and decays of pseudoscalar mesons in a nonrelativistic quark model with an idea abstracted from quantum chromodynamics

Abstract

The compositeness of mesons is taken into account in the evaluation of decays and mixing of eta, eta', and eta/sub c/ with an idea abstracted from quantum chromodynamics. Effective couplings of a pseudoscalar meson and two gluons are calculated in a simple model, where the Bethe-Salpeter amplitude is approximated in terms of harmonic-oscillator wave functions. The model is constructed so as to reproduce S-wave meson masses and the values of wave functions at the origin in the sense of the nonrelativistic quark model. In this model GAMMA (..pi../sup 0/ ..-->.. 2..gamma..) is reproduced satisfactorily. We obtain an s-dependent mixing angle, which is estimated to be - 42.3/sup 0/ and - 40.0/sup 0/ for s = M/sub eta//sup 2/ and s = M/sub etaprime//sup 2/, respectively. Criticism of various estimations of the angle is presented. All the results are shown to be consistent with experiments. The importance of the compositeness of mesons is stressed.