《in the Nlowast; program》.pdfVIP

Opportunities and Challenges for Theory in the N∗ program C. D. Roberts1,2,3,4 1 1Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA 1 2Institut für Kernphysik, Forschungszentrum Jülich, D-52425 Jülich, Germany 0 3Department of Physics, Illinois Institute of Technology, Chicago, Illinois 60616-3793, USA 2 4Department of Physics, Center for High Energy Physics and State Key Laboratory of Nuclear g Physics and Technology, Peking University, Beijing 100871, China u A Abstract. The N ∗-program provides a path to understanding the essentially-nonperturbative funda- 4 mentals at the heart of the Standard Model: confinement and dynamical chiral symmetry breaking. Relating this data to QCD’s basic degrees-of-freedom is a key challenge for theory. In tackling it, ] one steps immediately into the domain of relativistic quantum field theory where within the key h t phenomena can only be understood via nonperturbative methods. No one tool is yet fully equal to l- the challenge. Nonetheless, the last few years have seen significant progress in QCD-based theory, c and the reaction models necessary to bridge the gap between that theory and experiment. u n Keywords: Baryon and meson spectra, Baryon transition form factors, Confinement, Dynamical [ chiral symmetry breaking PACS: 12.38.Aw, 12.38.Lg, 13.40.-f, 14.20.Gk 1 v 0 1. Introduction Two key questions drive the international effort focused on the physics 3 0 of excited nucleons: Which hadron states and resonance