Spin Observables in Transition-Distribution-Amplitude Studies

TL;DR

This paper discusses how spin observables in exclusive hadronic reactions and electroproduction processes can help distinguish between different underlying mechanisms, emphasizing the role of transition distribution amplitudes (TDAs) in a partonic framework.

Contribution

It introduces the use of spin structure analysis and target-transverse-spin asymmetries to differentiate between partonic and baryon-exchange mechanisms in exclusive reactions.

Findings

Target-transverse-spin asymmetries are indicative of a partonic description.

Spin observables can disentangle mechanisms in exclusive reactions.

TDAs provide a framework for understanding spin effects in these processes.

Abstract

Exclusive hadronic reactions with a massive lepton pair (l^+l^-) in the final state will be measured with PANDA at GSI-FAIR and with Compass at CERN, both in p+p-bar -> l^+l^-+pi and pi+N -> N'+l^+l^-. Similarly, electroproduction of a meson in the backward region will be studied at JLAB. We discuss here how the spin structure of the amplitude for such processes will enable us to disentangle various mechanisms. For instance, target-transverse-spin asymmetries are specific of a partonic description, where the amplitude is factorised in terms of baryon to meson or meson to baryon Transition Distribution Amplitudes (TDAs) as opposed to what is expected from baryon-exchange contributions.