Studies of Nucleon Resonance Structure in Exclusive Meson Electroproduction

TL;DR

This paper discusses a high-Q2 experimental program at Jefferson Lab to study nucleon resonances through exclusive meson electroproduction, aiming to understand baryon structure and non-perturbative QCD dynamics.

Contribution

It presents a detailed experimental and theoretical framework for probing N* electrocouplings at unprecedented photon virtualities up to 12 GeV2.

Findings

First high-Q2 measurements of N* electrocouplings

Advances in reaction theory for meson electroproduction

Insights into confinement and chiral symmetry breaking

Abstract

Studies of the structure of excited baryons are key to the N* program at Jefferson Lab. Within the first year of data taking with the Hall B CLAS12 detector following the 12 GeV upgrade, a dedicated experiment will aim to extract the N* electrocouplings at high photon virtualities Q2. This experiment will allow exploration of the structure of N* resonances at the highest photon virtualities ever yet achieved, with a kinematic reach up to Q2 = 12 GeV2. This high-Q2 reach will make it possible to probe the excited nucleon structures at distance scales ranging from where effective degrees of freedom, such as constituent quarks, are dominant through the transition to where nearly massless bare-quark degrees of freedom are relevant. In this document, we present a detailed description of the physics that can be addressed through N* structure studies in exclusive meson electroproduction. The discussion includes recent advances in reaction theory for extracting N* electrocouplings from meson electroproduction off protons, along with QCD-based approaches to the theoretical interpretation of these fundamental quantities. This program will afford access to the dynamics of the non-perturbative strong interaction responsible for resonance formation, and will be crucial in understanding the nature of confinement and dynamical chiral symmetry breaking in baryons, and how excited nucleons emerge from QCD.