Ls. Celenza et al., Role of a covariant confinement model in the calculation of the two-photondecay of the eta and eta ', PHYS REV C, 59(3), 1999, pp. 1700-1707
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].