QCD factorization with heavy quarks

Recent improvements [1] of the next-to-leading log x (NLx) results [2] in the BFKL framework, have stabilized the small-x behaviour in QCD, so that a phenomenological analysis of deep inelastic processes (DIS) seems now possible. However, both the gluon density (satisfying the improved equation) and the impact factors are needed in order to use k-factorization [3] to compute DIS or double DIS processes. So far, NLx impact factors have been found for the unphysical case of massless initial quarks and gluons only [3,4]. Partial features for massive quarks [5,6] and for colourless sources [7] are known too. In this talk we present the complete results for the case of initial massive quarks derived in Ref. [8]. These results allowed us to check the validity of the k-factorization scheme introduced in Ref. [4], or, in other words, to derive probe independent gluon Green’s function with an explicit massive quark impact factor which satisfies the expected collinear properties. Furthermore, we developed as a byproduct some analytical techniques which are needed to deal with two-scale problems, which are hopefully useful to cope with the physical cases also.