Color-Octet

We study contributions from color-octet quarkonium formation mechanisms to J=/ hadroproduction at low p ? . We include transitions of color-octet c¯c states into "direct" J=/ and into Ø 1;2 which decay radiatively into a J=/. Together with earlier work, this calculation constitutes a complete analysis of p ? -integrated J=/ production at leading twist. We find that the leading-twist contribution is not sufficient to reproduce the observed production rates and polarization of the J=/ and Ø 1;2 . Hence there must exist other important quarkonium production mechanisms at low p ? . Typeset using REVT E X I. INTRODUCTION The production and decays of heavy quarkonia have been widely studied using perturbative QCD [1]. Due to the large masses of the c and b quarks, the production or annihilation of heavy-quark--antiquark pairs takes place at a much shorter timescale than the formation of the bound state. This makes it possible to factorize the transition amplitudes. In hadroproduction re..