Quark contribution to the Reggeon-Reggeon-gluon vertex in QCD

Abstract

The quark loop contribution to the Reggeon-Reggeon-gluon vertex is calculated in QCD, where the Reggeon is the Reggeized gluon. Compared with the vertex in the Born approximation, this contribution exhibits a new spin structure as well as the gluon loop one. A remarkable but not complete cancellation between gluon and quark contributions to this new spin structure takes place for the case of three massless quark flavors.