Quark-antiquark contribution to the multigluon amplitudes in the helicity formalism

Using the helicity formalism, we compute the contribution of a quark-antiquark pair to the tree-level multigluon amplitudes in the high-energy limit. The $\bar{q}\, q$-pair production is absent in the leading-log formalism, but contributes to the next-to-leading corrections to it, and is therefore relevant for the computation of parton-parton scattering in the high-energy limit and of the gluon anomalous dimension at small $x_{bj}$, at next-to-leading accuracy.