Nucleon Resonance Physics

Abstract

Recent results of meson photo-production at the existing electron machines with polarized real photon beams and the measurement of polarization observables of the final state baryons have provided high precision data that led to the discovery of new excited nucleon and $\Delta$ states using multi-channel partial wave analyses procedures. The internal structure of several prominent excited states has been revealed employing meson electroproduction processes. On the theoretical front, lattice QCD is now predicting the baryon spectrum with very similar characteristics as the constituent quark model, and continuum QCD, such as is represented in the Dyson-Schwinger Equations approach and in light front relativistic quark models, describes the non-perturbative behavior of resonance excitations at photon virtuality of $Q^2>1.5Ge{V}^2$. In this talk I discuss the need to continue a vigorous program of nucleon spectroscopy and the study of the internal structure of excited states as a way to reveal the effective degrees of freedom underlying the excited states and their dependence on the distance scale probed.

9 pages. 9 figures, ECT* 2015 Workshop on Nucleon Resonances, October 12-16, 2015, Trento, Italy

References in corpus (9)

• Big-Bang Nucleosynthesis
• 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
• Data analysis techniques, differential cross sections, and spin density matrix elements for the reaction $\gamma p\to \varphi p$
• 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

Cited by in corpus (10)

• Nucleon-to-Roper electromagnetic transition form factors at large-$Q^2$
• Dissecting nucleon transition electromagnetic form factors
• Evidence for the $N^{\prime }(1720)3/2^{+}$ Nucleon Resonance from Combined Studies of CLAS ${\pi }^{+}{\pi }^{-}p$ Photo- and Electroproduction Data
• First results on nucleon resonance photocouplings from the $\gamma p\to {\pi }^{+}{\pi }^{-}p$ reaction
• Spectrum and structure of octet and decuplet baryons and their positive-parity excitations
• N* Structure and Strong QCD
• Electromagnetic multipole moments of baryons
• Nucleon resonances with spin $\frac{3}{2}$ and isospin $\frac{1}{2}$
• Angular Distributions, Polarization Observables, Spin Density Matrices and Statistical Tensors in Photoproduction of Two Pseudoscalar Mesons off a Nucleon
• Valence-quark structure N* resonances from DSEs