Conformal couplings and ``azimuthal matching'' of QCD Pomerons

TL;DR

This paper explores the conformal invariance in perturbative QCD to derive couplings of external states to conformal spin components of the QCD Pomeron, highlighting the role of azimuthal matching in gamma*-proton scattering.

Contribution

It introduces a method to derive couplings of external states to all conformal spin components using asymptotic conformal invariance and discusses azimuthal matching in the context of the QCD Pomeron.

Findings

Maximal perturbative coupling for linear transverse photon polarization.

Azimuthal matching is crucial for the conjecture of a second QCD Pomeron.

Strong azimuthal matching of p=1 component supports the second Pomeron hypothesis.

Abstract

Using the asymptotic conformal invariance of perturbative QCD we derive the expression of the coupling of external states to all conformal spin-p components of the forward elastic amplitude. Using the wave-function formalism for structure functions at small x, we derive the perturbative coupling of the virtual photon for p= 1, which is maximal for linear transverse polarization. The non-perturbative coupling to the proton is discussed in terms of ``azimuthal matching'' between the proton color dipoles and the quark- antiquark configurations of the photon. As an application, the recent conjecture of a second QCD Pomeron related to the conformal spin-1 component is shown to rely upon a strong azimuthal matching of the p= 1 component in gamma* -proton scattering.