  Most previous calculations of the annihilation decay rates of heavy
quarkonium were based on factorization assumptions that were unproven and, in
some cases, even incorrect. The recent development of a general factorization
formula for heavy quarkonium annihilation rates has provided a rigorous
theoretical foundation for such calculations. The factorization formula is
based on the use of the effective field theory NRQCD to factor the decay rate
into short-distance coefficients that can be calculated in perturbation theory
and long-distance matrix elements that can be computed using lattice
simulations. This approach allows annihilation decay rates to be computed
entirely from first principles.
