Diffractive Structure Function in a Quasi-Classical Approximation

TL;DR

This paper derives a formula for the diffractive structure function at small x, showing its relation to inclusive processes and its dependence on the gluon distribution, highlighting diffraction as a leading twist effect.

Contribution

It provides a quasi-classical approximation for the diffractive F_2 structure function including multiple rescatterings, linking diffraction to gluon distributions at high Q^2.

Findings

Diffractive structure function is proportional to gluon distribution at high Q^2.

Relation established between diffractive and inclusive scattering processes.

Diffraction is shown to be a leading twist effect.

Abstract

We derive an expression for diffractive F_2 structure function which should be valid at small x for quasi-elastic scattering on a hadron and for quasi-elastic scattering on a large nucleus. This expression includes multiple rescatterings of the quark-antiquark pair produced by the virtual photon off the sources of color charge in a quasi-classical approximation. We find that there is a relation between such diffractive production and inclusive processes. In the former, one averages over all colors of sources before squaring the amplitude, and in the latter one first squares the amplitude and then averages it in the hadron's or nuclear wave function. We show that in the limit of a large virtuality of the photon Q^2 the diffractive structure function becomes linearly proportional to the gluon distribution of the hadron or nucleus, therefore proving that in this sense diffraction is a leading twist effect.