Color-singlet direct J/psi and psi ' production at the Fermilab Tevatron in the k(t) factorization approach - art. no. 034006

Direct J/psi and psi' production rates at the Fermilab Tevatron are calcula ted in the k(t)-factorization approach within the color-singlet model. In t his approach, the production rates are enhanced by a factor of about 20 com pared to the naive collinear parton model leading order calculations. Howev er, the theoretical predictions are still below the experimental data by at least one order of magnitude. This means that to explain charmonium produc tions at Tevatron, we still need to call for the contributions from color-o ctet channels or other production mechanisms.