Heavy-quark production with $k_t$-factorization: The importance of the sea-quark distribution

Abstract

We discuss the fact that $k_t$-factorization calculations for heavy-quark production include only the $gg\to Q\bar{Q}$ contribution. The cases of fixed-flavor-number scheme and variable-flavor-number scheme calculations are analyzed separately. For the latter, we show that, similarly to the collinear factorization, the main contribution is given by the $Qg\to Qg$ process. In this scheme, calculations including only the $gg$ contribution should show a large discrepancy with the data. We show that, if they do not, it is because they include (effectively) a large $K$ factor.

Comments: Important modifications, new figures are added. Published in Phys. Rev. D 99, 074006 (2019)