Chiral anomaly and high-energy scattering in QCD

Abstract

Infra-red properties of the triangle anomaly and the "anomaly pole" are elaborated and applied to the study of high-energy scattering in QCD, when the gauge symmetry is partially broken to SU(2). It is shown that the chiral flavor anomaly provides a wee-gluon component for Goldstone bosons that combines with interactions due to the U(1) anomaly to produce an infra-red transverse momentum scaling divergence in scattering amplitudes. After the divergence is factorized out, as a wee gluon condensate in the infinite momentum pion, the remaining physical amplitudes have confinement and chiral symmetry breaking. A lowest-order contribution to the pion scattering amplitude is calculated in detail. Although originating from very complicated diagrams, the amplitude has a remarkable (semi-)perturbative simplicity. The momentum structure is that of single gluon exchange but zero transverse momentum quarks inject additional spin and color structure via anomaly interactions.