ELECTROMAGNETIC ANNIHILATION RATES OF CHI(C0) AND CHI(C2) WITH BOTH RELATIVISTIC AND QCD RADIATIVE-CORRECTIONS

We estimate the electromagnetic decay rates of chi(c0)-->gamma gamma a nd chi c(2)-->gamma gamma by taking into account both relativistic and QCD radiative corrections. The decay rates are derived in the Bethe-S alpeter formalism and the QCD radiative corrections are included in ac cordance with the factorization assumption. Using a QCD-inspired inter quark potential, we obtain relativistic BS wave functions of chi(c0) a nd chi(c2) by solving the BS equation for the corresponding (2S+1)L(J) states. Our numerical result for the ratio R=Gamma(chi(c0)-->gamma ga mma)/Gamma(chi(c2)-->gamma gamma) is about 11-13, which agrees with th e update E760 experiment data. Explicit calculations show that in addi tion to the QCD radiative corrections which may increase the ratio R b y about a factor of 2, the relativistic corrections due to spin-depend ent interquark forces induced by gluon exchange also enhance the ratio R substantially and its value is insensitive to the choice of paramet ers that characterize the interquark potential. Our expressions for th e decay widths are identical with that obtained in the NRQCD theory to the next-to-leading order in upsilon(2) and alpha(s). Moreover, we ha ve determined two new coefficients in the nonperturbative matrix eleme nts for these decay widths.