2 00 3 Direct J / ψ and ψ ′ hadroproduction via fragmentation in the collinear parton model and k T - factorization approach

The p T-spectra for direct J/ψ and ψ ′ in hadroproduction at Tevatron energy have been calculated based on NRQCD formalism and fragmentation approximation in the collinear parton model and k T-factorization approach. We have described the CDF data and obtained a good agreement between the predictions obtained in the parton model and k T-factorization approach. We performed the calculations using the relevant leading order in α s hard amplitudes and the equal values of the color-octet long-distance matrix elements for the both models.