Role of a covariant confinement model in the calculation of the two-photondecay of the eta and eta '

We calculate the rate for the two-photon decay of the eta and eta' mesons i n a relativistic quark model which includes a model of confinement. [In the absence of the confinement model, our model reduces to the SU(3)-flavor Na mbu-Jona-Lasinio model supplemented by the 't Hooft interaction.] Since we have studied singlet-octet mixing for the eta and eta' in a previous work, we do not have any adjustable parameters in our calculations. The decay of the eta may be calculated with or without a confinement model for a fixed s et of parameters. In the absence of confinement, the width Gamma(eta-->gamm a gamma) is overestimated by a factor of 3 in our analysis. However, inclus ion of confinement then yields an excellent fit to the data for Gamma(eta-- >gamma gamma) and a value of Gamma(eta'-->gamma gamma) which is about 25% t oo small. While it is possible to fit Gamma(eta-->gamma gamma) without a co nfinement model, using modified values of the parameters, it is clear that a model of confinement is needed if we are to describe the properties of bo th the eta and eta' in calculations of the type considered here. [S0556-281 3(99)04803-7].