N* Structure and Strong QCD

Abstract

In attempting to match QCD with Nature, it is necessary to confront the many complexities of strong, nonlinear dynamics in relativistic quantum field theory, e.g. the loss of particle number conservation, the frame and scale dependence of the explanations and interpretations of observable processes, and the evolving character of the relevant degrees-of-freedom. The peculiarities of QCD ensure that it is also the only known fundamental theory with the capacity to sustain massless elementary degrees-of-freedom, gluons and quarks; and yet gluons and quarks are predicted to acquire mass dynamically so that the only massless systems in QCD are its composite Nambu-Goldstone bosons. All other everyday bound states possess nuclear-size masses, far in excess of anything that can directly be tied to the Higgs boson. These observations highlight fundamental questions within the Standard Model: what is the source of the mass for the vast bulk of visible matter in the Universe, how is its appearance connected with confinement; how is this mass distributed within hadrons and does the distribution differ from one hadron to another? This contribution sketches insights drawn using modern methods for the continuum bound-state problem in QCD, and how they have been informed by empirical information on the hadron spectrum and nucleon-to-resonance transition form factors.

21 pages, 6 figures, 1 table. Contribution to the proceedings of the 11th International Workshop on the Physics of Excited Nucleons, 20-23 August 2017, University of South Carolina, Columbia, SC, USA

References in corpus (26)

• Baryons as relativistic three-quark bound states
• The Deuteron Spin-dependent Structure Function g1d and its First Moment
• Bridging a gap between continuum-QCD and ab initio predictions of hadron observables
• Hadron Properties and Dyson-Schwinger Equations
• Abelian anomaly and neutral pion production
• pi- and rho-mesons, and their diquark partners, from a contact interaction
• A study of the $P_{11}(1440)$ and $D_{13}(1520)$ resonances from CLAS data on $ep\to e^{\prime }{\pi }^{+}{\pi }^{-}{p}^{\prime }$
• Pion form factor from a contact interaction
• Natural constraints on the gluon-quark vertex
• Determination of the effective strong coupling constant alpha_{s,g_1}(Q^2) from CLAS spin structure function data
• Extraction and Interpretation of gamma N --> Delta Form Factors within a Dynamical Model
• On light baryons and their excitations
• Gauge invariance of a critical number of flavours in QED3
• High precision determination of the $Q^2$-evolution of the Bjorken Sum
• Running coupling constant of ten-flavor QCD with the Schrödinger functional method
• Empirical transverse charge densities in the nucleon-to-P11(1440) transition
• Structure of the nucleon's low-lying excitations
• Light-cone Distribution Amplitudes of the Nucleon and Negative Parity Nucleon Resonances from Lattice QCD
• Study of the process $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}\eta$ using initial state radiation
• Parity partners in the baryon resonance spectrum
• Parton distribution amplitudes: revealing diquarks in the proton and Roper resonance
• Strong evidence for nucleon resonances near 1900\,MeV
• Dissecting nucleon transition electromagnetic form factors
• Leading-twist distribution amplitudes of scalar- and vector-mesons
• Kaon Distribution Amplitude from Lattice QCD and the Flavor SU(3) Symmetry
• Roper resonance -- solution to the fifty year puzzle

Cited by in corpus (14)

• Diquark Correlations in Hadron Physics: Origin, Impact and Evidence
• Spectrum of light- and heavy-baryons
• Nucleon-to-Roper electromagnetic transition form factors at large-$Q^2$
• Strong QCD Insights from Excited Nucleon Structure Studies with CLAS and CLAS12
• Nucleon elastic form factors at accessible large spacelike momenta
• Proton tensor charges from a Poincaré-covariant Faddeev equation
• The ghost-antighost-gluon vertex from the Curci-Ferrari model: Two-loop corrections
• Transition form factors: ${\gamma }^{\ast }+p\to \Delta (1232)$, $\Delta (1600)$
• New Perspective on Hybrid Mesons
• Practical scheme from QCD to phenomena via Dyson-Schwinger equations
• Spontaneous chiral symmetry breaking in the massive Landau gauge: realistic running coupling
• Transition form factors and helicity amplitudes for electroexcitation of negative- and positive parity nucleon resonances in a light-front quark model
• Excited Nucleon Spectrum and Structure Studies with CLAS and CLAS12
• Constraining the Hadron-Quark Phase Transition Chemical Potential via Astronomical Observation