Measurement of Deeply Virtual Compton Scattering at HERA

TL;DR

This paper reports the first differential measurement of elastic deeply virtual Compton scattering at HERA, analyzing how the cross section varies with photon virtuality, invariant mass, and momentum transfer, and compares results with QCD models.

Contribution

It provides the first differential cross section measurements of DVCS as a function of t at HERA, testing QCD predictions with experimental data.

Findings

QCD NLO calculations describe the data well.

Color dipole models also agree with measurements.

Cross sections vary with Q^2, W, and t as predicted.

Abstract

A measurement is presented of elastic deeply virtual Compton scattering \gamma* p \to \gamma p made using e^+ p collision data corresponding to a luminosity of 46.5 pb^{-1}, taken with the H1 detector at HERA. The cross section is measured as a function of the photon virtuality, Q^2, the invariant mass of the \gamma* p system, W, and for the first time, differentially in the squared momentum transfer at the proton vertex, t, in the kinematic range 2 < Q^2 < 80 GeV^2, 30 < W < 140 GeV and |t| < 1 GeV^2. QCD based calculations at next-to-leading order using generalized parton distributions can describe the data, as can colour dipole model predictions.