Bulletin of the American Physical Society
APS April Meeting 2014
Volume 59, Number 5
Saturday–Tuesday, April 5–8, 2014; Savannah, Georgia
Session E10: Invited Session: Light Baryons as Few-Body Systems |
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Sponsoring Units: GFB Chair: Martin Savage, University of Washington Room: 204 |
Saturday, April 5, 2014 3:30PM - 4:06PM |
E10.00001: Nucleon and Delta structure in continuum QCD Invited Speaker: Ian Cloet Quantum Chromodynamics (QCD) is the only known example in nature of a fundamental quantum field theory that is innately non-perturbative. Solving QCD will have profound implications for our understanding of the natural world, for example, it will explain how light quarks and massless gluons bind together to form the observed mesons and baryons; hence explaining the origin of more than 98\% of the mass in the visible universe. Given the challenges posed by QCD, it is insufficient to study hadron ground-states alone if one seeks a solution; in this regard the delta plays a special role as the lightest baryon resonance. I will discuss recent progress using continuum QCD approaches to the study of nucleon and delta properties, with a focus on insights gained by the calculation (and measurement) of their electromagnetic form factors. [Preview Abstract] |
Saturday, April 5, 2014 4:06PM - 4:42PM |
E10.00002: What Nucleons Resonances Teach Us About the Nucleon Structure Invited Speaker: Volker D. Burkert The excitation spectrum of atomic hydrogen contains the full information needed to describe its structure from its basic ingredients, protons and electrons, and the electromagnetic interaction between them. Similarly, the nucleon excitation spectrum contains information about the effective degrees of freedom and the forces between them. The difference between the two systems is that in the former case the electromagnetic interaction leads to a well-defined energy spectrum, while the latter has strongly interacting ingredients, hadrons, quarks and gluons, at its core leading to broad and overlapping energy levels that in most cases cannot be studied in isolation. Microscopic approaches such as modern constituent quark models and Lattice QCD, make predictions regarding masses and quantum numbers of the excited states and their internal structure according to radial, spin, and orbital transitions of the quark-gluon system. Pion induced transitions have revealed many states largely consistent with these predictions, but many of the predicted states have not been observed. The quest for a better understanding of the internal structure of nucleons has led to a worldwide effort to measure nucleon excitations using photon- and electron-induced processes and to determine their internal structure. At Jefferson Lab with the CLAS detector differential cross sections and polarization observables have been measured with unprecedented precision and some of these data have been analyzed with modern coupled channel approaches that led to evidence of a number of previously unobserved excited states. In this talk, I discuss the two main directions of current experimental research, the search for new states in meson photoproduction and the study of resonance transition form factors in electroproduction, which encode the internal structure and the nature of the excited states. [Preview Abstract] |
Saturday, April 5, 2014 4:42PM - 5:18PM |
E10.00003: Nucleon Structure on the Light-Front Invited Speaker: Christian Weiss The light-front (or partonic) view of relativistic dynamics enables a description of hadrons as composite many-body systems that shows many analogies with traditional few-body systems (atoms, nuclei). It defines the spatial structure of hadrons and allows one to study the space-time evolution of strong and electromagnetic processes. Light-front methods represent an essential tool in the theory and phenomenology of nucleon structure and are used both in QCD and in formulations based on effective degrees of freedom. In this talk we explain the physical picture and highlight several novel applications. This includes (a) the transverse charge and current densities measured in elastic eN scattering and their interpretation; (b) the study of peripheral spatial nucleon structure using chiral effective field theory; (c) resonance structure on the light-front; (d) the mapping of the spatial distributions of QCD quarks and gluons (Generalized Parton Distributions, or GPDs) in the nucleon using exclusive processes at multi-GeV momentum transfer. [Preview Abstract] |
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