Opportunities and Challenges for Theory in the N* program

TL;DR

This paper discusses the progress and challenges in developing theoretical approaches to understand fundamental nonperturbative phenomena in QCD, such as confinement and chiral symmetry breaking, through the N*-program.

Contribution

It highlights recent advances in QCD-based theory and reaction models that connect experimental data to the underlying degrees of freedom in the Standard Model.

Findings

Significant progress in nonperturbative QCD methods

Development of reaction models bridging theory and experiment

Ongoing challenges in fully understanding confinement and chiral symmetry breaking

Abstract

The N*-program provides a path to understanding the essentially-nonperturbative fundamentals at the heart of the Standard Model: confinement and dynamical chiral symmetry breaking. Relating this data to QCD's basic degrees-of-freedom is a key challenge for theory. In tackling it, one steps immediately into the domain of relativistic quantum field theory where within the key phenomena can only be understood via nonperturbative methods. No one tool is yet fully equal to the challenge. Nonetheless, the last few years have seen significant progress in QCD-based theory, and the reaction models necessary to bridge the gap between that theory and experiment.