Direct J/psi hadroproduction in k(perpendicular to) factorization and the color octet mechanism - art. no. 077501

The hadroproduction of direct J/psi, in the framework of the k(perpendicula r to)-factorization approach is studied. The color-singlet contribution is essentially larger than in the collinear approach but is still an order of magnitude below the data. The deficit may be well described by the color oc tet contribution with the value of the matrix element (0 \O-8(J/psi)(S-3(1) )\0) substantially decreased in comparison with fits in the collinear facto rization. This should lead to a reduction of the large transverse polarizat ion, predicted in the collinear approach.