Power corrections in a transverse-momentum cut for vector-boson production at NNLO: the qg-initiated real-virtual contribution

We consider the production of a vector boson (Z, W± or γ∗) at next-to-next-to-leading order in the strong coupling constant αS. We impose a transverse-momentum cutoff, qTcut, on the vector boson produced in the qg-initiated channel. We then compute the power corrections in the cutoff, up to the second power, of the real-virtual interference contribution to the cumulative cross section at order αS2. Other terms with the same kinematics, originating from the subtraction method applied to the double-real contribution, have been also considered. The knowledge of such power corrections is a required ingredient in order to reduce the dependence on the transverse-momentum cutoff of the QCD cross sections at next-to-next-to-leading order, when the qT-subtraction method is applied. In addition, the study of the dependence of the cross section on qTcut allows as well for an understanding of its behaviour in the small transverse-momentum limit, giving hints on the structure at all orders in αS and on the identification of universal patterns. Our result are presented in an analytic form, using the process-independent procedure described in a previous paper for the calculation of the all-order power corrections in qTcut.