Renormalon ambiguities in NRQCD operator matrix elements - art. no. 054008

We analyze the renormalon ambiguities that appear in factorization formulas in PCD. Our analysis contains a simple argument that the ambiguities in th e short-distance coefficients and operator matrix elements are artifacts of dimensional-regularization factorization schemes and are absent in cutoff schemes. We also present a method for computing the renormalon ambiguities in operator matrix elements and apply it to a computation of the ambiguitie s in the matrix elements that appear in the NRQCD factorization formulas fo r the annihilation decays of S-wave quarkonia. Our results, combined with t hose of Braaten and Chen for the short-distance coefficients, provide an ex plicit demonstration that the ambiguities cancel in the physical decay rate s. In addition, we analyze the renormalon ambiguities in the Gremm-Kapustin relation and in various definitions of the heavy-quark mass. [S0556-2821(9 9)03813-8].