Z-boson production in association with heavy flavor in the kT-factorization

Abstract

We present the calculations of associated production of Z bosons and heavy (charm or beauty) quarks at the LHC energies in the framework of kT -factorization QCD approach. Our consideration is mainly based on the O α α s 2 off-shell gluon-gluon fusion subprocess g*g*→ZQ Q ̅ where produced Z boson subsequently decays into a lepton pair. Several subleading contributions from the O α α s 2 and O α α s 3 subprocesses are taken into account. Contributions from the double parton scattering mechanism are estimated. The transverse momentum dependent (or unintegrated) gluon densities in a proton are determined using the Catani-Ciafaloni-Fiorani-Marchesini evolution equation. We achieve reasonably good agreement of our predictions and latest experimental data taken by the CMS and ATLAS Collaborations, discuss the theoretical uncertainties of our calculations and demonstrate the importance of subleading quark contributions in description of the LHC data in the whole kinematical region.