Measurement of Diffractive Scattering of Photons with Large Momentum Transfer at HERA

TL;DR

This paper reports the first measurement of diffractive scattering of quasi-real photons with large momentum transfer at HERA, analyzing cross sections as functions of energy and momentum transfer, and comparing results to perturbative QCD models.

Contribution

It provides the first experimental measurement of gamma p -> gamma Y diffractive scattering at large momentum transfer, testing perturbative QCD predictions.

Findings

W dependence matches BFKL-based model

|t| dependence is harder than model predictions

Results extend understanding of diffractive photon scattering

Abstract

The first measurement of diffractive scattering of quasi-real photons with large momentum transfer gamma p -> gamma Y, where Y is the proton dissociative system, is made using the H1 detector at HERA. The measurement is performed for initial photon virtualities Q^2 < 0.01 GeV^2. Cross sections are measured as a function of W, the incident photon-proton entre of mass energy, and t, the square of the four-momentum transferred at the proton vertex, in the range 175 < W < 247 GeV and 4<|t|<36 GeV^2. The W dependence is well described by a model based on perturbative QCD using a leading logarithmic approximation of the BFKL evolution. The measured |t| dependence is harder than that predicted by the model and those observed in exclusive vector meson production.