Studying the Perturbative Reggeon

TL;DR

This paper develops a numerical method to solve the perturbative QCD equations for the flavour non-singlet Reggeon, revealing how running coupling and non-perturbative effects influence its behavior at low Bjorken-x.

Contribution

It introduces a novel numerical approach for solving the Reggeon amplitude equations, incorporating running coupling and non-perturbative mass effects.

Findings

Sharp rise in amplitude at low x with running coupling

Enhanced rise due to running coupling effects

Suppressed Q^2 dependence with running coupling

Abstract

We consider the flavour non-singlet Reggeon within the context of perturbative QCD. This consists of ladders built out of ``reggeized'' quarks. We propose a method for the numerical solution of the integro-differential equation for the amplitude describing the exchange of such a Reggeon. The solution is known to have a sharp rise at low values of Bjorken-x when applied to non-singlet quantities in deep-inelastic scattering. We show that when the running of the coupling is taken into account this sharp rise is further enhanced, although the Q^2 dependence is suppressed by the introduction of the running coupling. We also investigate the effects of simulating non-perturbative physics by introducing a constituent mass for the soft quarks and an effective mass for the soft gluons exchanged in the t-channel.