Timelike Virtual Compton Scattering from Electron-Positron Radiative Annihilation

TL;DR

This paper proposes a method to measure the timelike deeply virtual Compton scattering amplitude in electron-positron colliders through radiative annihilation, enabling new insights into hadron structure and form factors.

Contribution

It introduces a novel approach to access timelike DVCS amplitudes via e+ e- annihilation, including interference effects and the role of the J=0 fixed pole.

Findings

Feasible measurement of timelike DVCS at electron-positron colliders.

Interference effects reveal phase information of the DVCS amplitude.

Model example illustrating the significance of the J=0 fixed pole.

Abstract

We propose measurements of the deeply virtual Compton amplitude (DVCS), gamma* to H H-bar gamma, in the timelike t = (p_{H} + p_{H-bar})^2 > 0 kinematic domain which is accessible at electron-positron colliders via the radiative annihilation process e+ e- to H H-bar gamma. These processes allow the measurement of timelike deeply virtual Compton scattering for a variety of H H-bar hadron pairs such as pi+ pi-, K+ K-, and D D-bar as well as p p-bar. As in the conventional spacelike DVCS, there are interfering coherent amplitudes contributing to the timelike processes involving C= - form factors. The interference between the amplitudes measures the phase of the C=+ timelike DVCS amplitude relative to the phase of the timelike form factors and can be isolated by considering the forward-backward e+ \leftrightarrow e- asymmetry. The J=0 fixed pole contribution which arises from the local coupling of the two photons to the quark current plays a special role. As an example we present a simple model.