N* Experiments and their Impact on Strong QCD Physics

Abstract

I give a brief overview of experimental studies of the spectrum and the structure of the excited states of the nucleon and what we learn about their internal structure. The focus is on the effort to obtain a more complete picture of the light-quark baryon excitation spectrum employing electromagnetic beams, and on the study of the transition form factors and helicity amplitudes and their dependence on the magnitude of the photon virtuality $Q^2$, especially for some of the most prominent resonances. The results were obtained in pion and eta electroproduction experiments off proton targets. They strengthen the connection of experiment and new results from modeling sQCD in DSE and Light Cone SR approaches. They also point to the nature of these states as 3-quark excitations at the core.

Introductory talk presented at the International workshop N*2017, University of South Carolina, Columbia, USA; 17 pages, 12 figures. arXiv admin note: text overlap with arXiv:1603.00919

References in corpus (10)

• Additional Strange Hadrons from QCD Thermodynamics and Strangeness Freeze-out in Heavy Ion Collisions
• A study of the $P_{11}(1440)$ and $D_{13}(1520)$ resonances from CLAS data on $ep\to e^{\prime }{\pi }^{+}{\pi }^{-}{p}^{\prime }$
• Dynamical Coupled-Channel Model of $\pi N$ Scattering in the W $\le$ 2 GeV Nucleon Resonance Region
• The melting and abundance of open charm hadrons
• A systematic study of longitudinal and transverse helicity amplidutes in the hypercentral Constituent Quark Model
• Measurements of $ep\to e^{\prime }{\pi }^{+}n$ at W = 1.6 - 2.0 GeV and extraction of nucleon resonance electrocouplings at CLAS
• Empirical transverse charge densities in the nucleon-to-P11(1440) transition
• Electroproduction of the Roper resonance on the proton: the role of the three-quark core and the molecular N-sigma component
• Electromagnetic Nucleon-to-Delta Transition in Holographic QCD
• Photon beam asymmetry $\Sigma$ in the reaction $\vec{\gamma }p\to p\omega$ for $E_{\gamma }$ = 1.152 to 1.876 GeV

Cited by in corpus (11)

• 50 Years of Quantum Chromodynamics
• Etaprime and Eta Mesons with Connection to Anomalous Glue
• Nucleon-to-Roper electromagnetic transition form factors at large-$Q^2$
• Strong QCD Insights from Excited Nucleon Structure Studies with CLAS and CLAS12
• Transition form factors: ${\gamma }^{\ast }+p\to \Delta (1232)$, $\Delta (1600)$
• Spectrum and structure of octet and decuplet baryons and their positive-parity excitations
• Spectroscopy of light $N^{\ast }$ baryons
• Transition form factors and helicity amplitudes for electroexcitation of negative- and positive parity nucleon resonances in a light-front quark model
• Exclusive ${\mathbf{\pi }}^0\mathbf{p}$ electroproduction off protons in the resonance region at photon virtualities 0.4~GeV${}^2$ $\le {\mathbf{Q}}^2\le 1$~GeV${}^2$
• Nucleon resonance production in the $\gamma p\to p\eta \varphi$ reaction
• Excited Nucleon Spectrum and Structure Studies with CLAS and CLAS12