Towards a solution of the charmonium production controversy: k( perpendicular) factorization versus color-octet mechanism.

ABSTRACT

The cross section of chi(cJ) hadroproduction is calculated in the k( perpendicular)-factorization approach. We find a significant contribution of the chi(c1) state due to non-applicability of the Landau-Yang theorem because of off-shell gluons. The results are in agreement with data and, in contrast to the collinear factorization, show a dominance of the color-singlet part and a strong suppression of the color octet contribution. Our results could therefore lead to a solution of the long-standing controversy between the color-singlet model and the color-octet mechanism.