Light quarks and the pomeron in QCD

Abstract

It is argued that light quarks are essential for the occurrence in QCD of a low transverse momentum Pomeron compatible with confinement and other well-established physical properties. It is shown that massless quark-loop interactions for reggeized gluons can be extracted from quark reggeon diagrams. These interactions are then shown to play a vital role in producing confinement from the exponentiation of infrared divergences of the gluon reggeon diagrams of SU(2) gauge theory. This form of confinement is dominant when there is a large number of massless quarks and is argued to be associated directly with the regularization of the massless quark sea in the presence of the anomaly. Fundamental features of the argument are the conflict of the necessary transverse momentum cut-off with Pauli-Villars regularization and the origin of a reggeon condensate in triangle anomaly transverse momentum divergences. The outcome is that SU(2) gauge theory has a high-energy limit closely analogous to the two-dimensional Schwinger model, that is the physical states are pseudoscalar mesons and the S-Matrix is “trivial” in the extreme sense that there is no Pomeron. Extension of the analysis to higher gauge groups shows that there is an even-signature Pomeron in QCD, anadditional Odderon trajectory in SU(4) gauge theory and N-2 trajectories in SU(N) gauge theory. Implications of the analysis for QCD with a small number of flavor and for the existence of a higher color quark sector associated with electroweak symmetry breaking are also discussed. * Work supported by the U.S. Department or Energy, Division of High Energy Physics, Contract W-31-109-ENG-38.