Accessing DEMP and DVCS at Backward Angles above the Resonance Region

TL;DR

This study proposes a dedicated measurement of exclusive electroproduction at backward angles above the resonance region to explore nucleon structure and test competing theoretical models related to QCD and nucleon substructure.

Contribution

It introduces a novel experimental approach to investigate backward angle meson production, applying the L/T separation method in an unexplored kinematic region to differentiate between theoretical models.

Findings

Potential to distinguish between GPD-like TDA and Regge models.

Insights into the transition from meson-nucleon to quark-hadron degrees of freedom.

Advancement in understanding nucleon structure at high momentum transfer.

Abstract

The proposed measurement is a dedicated study to investigate the exclusive electroproduction process: 1H(e, e'p)X, in the backward angle above the resonance region. Here, the produced particle X (pi0 or gamma) is emitted 180 degrees opposite to the virtual photon momentum. This study will apply the well-known L/T separation method of the electroproduction process to this unexplored backward angle kinematics region. The available theoretical frameworks give parallel interpretations to the backward angle meson production at the proposed kinematics. According to the QCD GPD-like TDA model, backward meson production as the virtual-photon probes the transverse meson cloud structure inside of the nucleon; whereas the hadronic Regge based model describes backward meson production as the interference between nucleon exchange and the meson produced via re-scattering of the nucleon. Testing these two approaches is like testing the onset of quarks and gluon physics, i.e. going deeper into the structure of nucleon to probe its quark and gluon content. Combining knowledge from both frameworks has the potential to provide complementary knowledge to the forward angle physics programs and obtain new physics insights to study the QCD transition from meson-nucleon to quark-hadron degrees of freedom.