\ga\ga and g g decay rates for equal mass heavy quarkonia

Abstract

We present a calculation of the two-photon and two-gluon widths for the equal mass quarkonium states ${}^1{S}_0$, ${}^3{P}_0$ and ${}^3{P}_2$ of the charmonium and upsilon systems. The approach taken is based on using the full relativistic $q\bar{q}\to \text{ga}\text{ga}$ amplitude together with a wave function derived from the instantaneous Bethe-Salpeter equation. Momentum space radial wave functions obtained from an earlier fit of the charmonium and upsilon spectra are used to evaluate the necessary integrals.

Comments: 6 pages, QCD corrections added, Tables modified