Hard Break-Up of Two-Nucleons and QCD Dynamics of NN Interaction

TL;DR

This paper reviews recent theoretical advances in high-energy two-nucleon break-up reactions, emphasizing the hard rescattering model's role in understanding QCD dynamics and experimental helicity effects.

Contribution

It introduces the hard rescattering model for describing high-energy two-nucleon break-up and predicts a new helicity selection mechanism confirmed by experiments.

Findings

Validation of the hard rescattering model in describing NN break-up.

Prediction and experimental confirmation of a new helicity selection mechanism.

Sensitivity of reactions to the dynamics of hard pn and pp interactions.

Abstract

We discus recent developments in theory of high energy two-body break-up of few-nucleon systems. The characteristics of these reactions are such that the hard two-body quasielastic subprocess can be clearly separated from the accompanying soft subprocesses. We discuss in details the hard rescattering model(HRM) in which hard photodisintegration develops in two stages. At first, photon knocks-out an energetic quark which rescatters subsequently with a quark of the other nucleon. The latter provides a mechanism of sharing the initial high momentum of the photon between two outgoing nucleons. This final state hard rescattering can be expressed through the hard NN scattering amplitude. Within HRM we discuss hard break-up reactions involving D and 3He targets and demonstrate how these reactions are sensitive to the dynamics of hard pn and pp interaction. Another development of HRM is the prediction of new helicity selection mechanism for hard two-body reactions, which was apparently confirmed in the recent JLab experiment.