Study of excited nucleons and their structure

Recent advances in the study of excited nucleons are discussed. Much of the progress has been achieved due to the availability of high precision meson production data in the photoproduction and electroproduction sectors, the development of multi-channel partial wave analysis techniques, and advances in Lattice QCD with predictions of the full excitation spectrum.Comment: 6 pages, 4 figures, Invited talk at NSTAR 201

Excitation of Nucleon Resonances

I discuss developments in the area of nucleon resonance excitations that are necessary to bring our understanding of nucleon structure in the regime of strong QCD to a qualitatively new level. They involve the collection of high quality data in various channels, a more rigorous approach in the search for "missing" quark model states, an effort to compute some critical quantities in nucleon resonance excitations from first principles, i.e. QCD, and a proposal aimed at obtaining an understanding of a fundamental quantity in nucleon structure.Comment: 9 pages, 2 figure

Probing the Structure of Nucleons in the Resonance Region with CLAS at Jefferson Lab

The physics of electromagnetic excitation of nucleon resonances and of their relevance in nucleon structure studies are discussed. Preliminary data from the CLAS detector on the N-Delta(1232) transition multipoles, the helicity amplitudes of the N*(1535), and the search for so-called "missing resonances" at Jefferson Lab are presented.Comment: Talk presented at Few Body Problems in Physics, Taipei, March 6-10, 2000, 10 pages, 8 figure

Spin Physics in the Resonance Region

Recent results from Jefferson Lab on measurement of inclusive double polarization asymmetries in the nucleon resonance region are discussed. Preliminary results on the first moment of the structure function g_1(x,Q^2) for protons, and on the generalized Gerasimov-Drell-Hearn integral for neutrons are presented as well. The first moment for protons shows a strong Q^2 dependence below Q^2 = 1 GeV^2, and changes sign near Q^2 = 0.3 GeV^2. Strong double polarization asymmetries are observed in exclusive electroproduction of pions from polarized protons.Comment: 9 pages, 6 figures, Talk presented at the 3rd International Conference on Perspectives in Hadronic Physics, Trieste May 7-11, 200

Strangeness Physics with CLAS at JLab

A brief overview of strangeness physics with the CLAS detector at JLab is given, mainly covering the domain of nucleon resonances. Several excited states predicted by the symmetric constituent quark model may have significant couplings to the K-Lambda or K-Sigma channels. I will discuss data that are relevant in the search for such states in the strangeness channel, and give an outlook on the future prospects of the N* program at JLab with electromagnetic probes.Comment: 9 pages, 7 figures, Conference on Strangeness in Nuclei, SENDAI 200

Probing the Structure of Nucleons in the Resonance Region

Status, open questions, and future prospects of the physics of excited nucleons are discussed. Emphasis is on the study of the structure of nucleons via measurements of their electromagnetic transition form factors, the search for "missing" resonances, the spin structure of the nucleon in the resonance region, and connections between the resonance and the deep-inelastic regimes.Comment: 13 pages, 7 figures, talk presented at NSTAR200

Spin Response of the Nucleon in the Resonance Region

I discuss recent results from Jefferson Lab on the measurement of inclusive spin structure functions in the nucleon resonance region using polarized electron beams and polarized targets. Results on the first moment of the spin structure function for protons and neutrons are discussed, as well as the Bjorken integral. I will argue that the helicity structure of individual resonances plays a vital role in understanding the nucleon's spin response in the domain of strong interaction QCD, and must be considered in any analysis of the nucleon spin structure at low and intermediate photon virtuality.Comment: 10 pages, 7 figures. Talk presented at the Second Asia Pacific Conference on Few Body Problems in Physics, Shanghai, China, August 27-30, 200