Regge Asymptotics of Scattering with Flavour Exchange in QCD

TL;DR

The paper develops a conformal-symmetry framework for flavour-exchange Regge dynamics in perturbative QCD, extending gluon-exchange methods to the exchange of two reggeized fermions with opposite helicity where double-logarithmic contributions prevail. It derives a partial-wave equation for the universal two-reggeon Green function, reformulates it in impact-parameter space with holomorphic factorization, and diagonalizes it using conformal representations. The leading Regge structure at large momentum transfer is computed, showing a dominant $n=0$ double-log trajectory and moving Regge poles under running coupling, with explicit expressions for the leading poles in $n=0,\pm1$ channels. These results clarify the Regge singularity landscape in flavour-exchange channels and provide a robust, symmetry-based method applicable to multi-reggeon exchanges and potential nonperturbative refinements.

Abstract

The contribution to the perturbative Regge asymptotics of the exchange of two reggeized fermions with opposite helicity is investigated. The methods of conformal symmetry known for the case of gluon exchange are extended to this case where double-logarithmic contributions dominate the asymptotics. The Regge trajectories at large momentum transfer are calculated.