What is Measured in Hard Exclusive Electroproduction?

TL;DR

This paper investigates the interpretation of amplitudes in hard exclusive electroproduction, revealing that at high energy and small momentum transfer, these are dominated by the meson cloud's quark content rather than the nucleon itself, challenging QCD scaling expectations.

Contribution

It clarifies the dominant physical contributions to exclusive electroproduction amplitudes at high energy, emphasizing the role of Regge amplitudes and meson cloud effects.

Findings

Amplitudes are dominated by meson cloud quark content at high energy.

Regge amplitudes significantly contribute to exclusive processes.

QCD scaling is violated in this regime.

Abstract

We examine the relation between amplitudes measured in exclusive lepto-production and the quark content of the nucleon. We show that in the limit of high energy and small t, the natural interpretation of amplitudes measured in these hard exclusive processes is in terms of the quark content of the meson cloud and not the target itself. In this regime, Regge amplitudes will make a significant contribution to these exclusive amplitudes. This leads to violation of QCD scaling.