Analyticity and Regge asymptotics in virtual Compton scattering on the nucleon

TL;DR

This paper tests the consistency of nucleon structure function data with analyticity and Regge asymptotics in virtual Compton scattering, deriving bounds that support the dominance of leading Reggeon contributions at high energies.

Contribution

It introduces a functional extremal problem approach to derive bounds on the Compton amplitude, providing evidence for Reggeon dominance in nucleon structure functions.

Findings

Lower bounds decrease with higher energy thresholds

Data are consistent with leading Reggeon asymptotics

Method estimates the subtraction constant reasonably

Abstract

We test the consistency of the data on the nucleon structure functions with analyticity and the Regge asymptotics of the virtual Compton amplitude. By solving a functional extremal problem, we derive an optimal lower bound on the maximum difference between the exact amplitude and the dominant Reggeon contribution for energies $\nu$ above a certain high value $\nu_h(Q^2)$. Considering in particular the difference of the amplitudes $T_1^\inel(\nu, Q^2)$ for the proton and neutron, we find that the lower bound decreases in an impressive way when $\nu_h(Q^2)$ is increased, and represents a very small fraction of the magnitude of the dominant Reggeon. While the method cannot rule out the hypothesis of a fixed Regge pole, the results indicate that the data on the structure function are consistent with an asymptotic behaviour given by leading Reggeon contributions. We also show that the minimum of the lower bound as a function of the subtraction constant $S_1^\inel(Q^2)$ provides a reasonable estimate of this quantity, in a frame similar, but not identical to the Reggeon dominance hypothesis.