Charm content of a proton in collinear parton model and in k_T-factorization approach

Abstract

It is shown that the difference between the c-quark proton structure functions calculated in the k_T-factorization approach using different unintegrated gluon distribution functions is the same order as the difference between results obtained in the parton model and in the k_T-factorization approach.

7 pages, Latex, 1 ps figures, epsf.sty