Heavy Quark Impact Factor at Next-to-leading Level

TL;DR

The paper addresses constructing the next-to-leading NLx heavy-quark impact factor within k-factorization for high-energy QCD processes. It develops a two-scale calculation using Mellin transforms and extends the Ciafaloni–Colferai CC factorization scheme to massive quarks, showing the gluon Green's function remains the same as in the massless case. The authors obtain a finite, factorized heavy-quark NLx impact factor, with single-logarithmic collinear divergences and a mass-dependent finite piece, validating a scale choice $s_0=\max(k_1,m_1)\max(k_2,m_2)$ that subtracts high-energy logarithms. The work confirms the universality of the subleading $H$-kernels and provides methods that could aid in deriving explicit DIS heavy-quark impact factors in two-scale problems.

Abstract

We further analyze the definition and the calculation of the heavy quark impact factor at next-to-leading (NL) log(s) level, and we provide its analytical expression in a previously proposed k-factorization scheme. Our results indicate that k-factorization holds at NL level with a properly chosen energy scale, and with the same gluonic Green's function previously found in the massless probe case.