An Analysis of Diffraction in Deep-Inelastic Scattering

TL;DR

This work develops a perturbatively motivated parametrization of the diffractive DIS cross section, decomposing $F_2^D$ into four components linked to different final states and twist levels, with explicit $Q^2$, β, and $x_{IP}$ dependencies guided by light-cone photon wave functions and two-gluon exchange. The authors fit the model to 1994 ZEUS and H1 data, finding that ZEUS data can be described without invoking a hard gluon in the Pomeron, while H1 data permit two solutions: one compatible with a singular gluon distribution (β≈1) and another resembling the ZEUS-driven scenario with a harder gluon component. The analysis reveals a characteristic β-dependent decomposition: low β from $q\bar{q}g$, mid β from transverse $q\bar{q}$, and high β from longitudinal $q\bar{q}$, highlighting the mixed soft/hard nature of diffraction and constraining the Pomeron’s partonic content. Overall, the two-gluon Pomeron framework can describe both datasets, though the H1 results leave open the question of a singular gluon distribution, calling for further tests in vector-meson production and diffractive jet analyses.

Abstract

We propose a simple parametrization for the deep-inelastic diffractive cross section. It contains the contribution of $q\bar{q}$ production to both the longitudinal and the transverse diffractive structure functions, and of the production of $q\bar{q}g$ final states from transverse photons. We start from the hard region and perform a suitable extrapolation into the soft region. We test our model on the 1994 ZEUS and H1 data, and confront it with the H1 conjecture of a singular gluon distribution.

Figures (9)

• Figure 1: Wave function of the photon, including (a) a $q {\bar{q}}$ component, and (b) a $q {\bar{q}} g$ component.
• Figure 2: Interaction with the proton, modelled in the two-gluon exchange approximation.
• Figure 3: Two-jet production in the $\gamma^*$-$I\!\!P$ center-of-mass system
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