The N* Physics Program at Jefferson Lab

Abstract

Recent measurements of nucleon resonance transition form factors with CLAS at Jefferson Lab are discussed. The new data confirm the assertion of the symmetric constituent quark model of the Roper as the first radial excitation of the nucleon. For the first time, the longitudinal transition amplitude to the S11(1535) was extracted from the data. New results on the transition amplitudes for the D13(1520) resonance are presented showing a rapid transition from helicity 3/2 dominance seen at the real photon point to helicity 1/2 dominance at higher Q2. I also discuss aspects of the JLab program to search for new excited nucleon states predicted by quark models.

8 pages, 14 figures, to be published in proceedings of NSTAR 2009, Beijing April 19-22, 2009

References in corpus (18)

• Unitary Isobar Model - MAID2007
• First Measurement of Beam-Recoil Observables Cx and Cz in Hyperon Photoproduction
• Measurement of the N to Delta(1232) Transition at High Momentum Transfer by pi0 Electroproduction
• Q^2 Dependence of the S_{11}(1535) Photocoupling and Evidence for a P-wave resonance in eta electroproduction
• The nucleon to Delta electromagnetic transition form factors in lattice QCD
• Electroexcitation of the Roper resonance for 1.7 < Q2 < 4.5 GeV2 in ep -> enpi+
• Experimental study of isovector spin sum rules
• Separated Structure Functions for the Exclusive Electroproduction of $K^{+}\Lambda$ and $K^{+}{\Sigma }^0$ Final States
• Single pi+ Electroproduction on the Proton in the First and Second Resonance Regions at 0.25GeV^2 < Q^2 < 0.65GeV^2 Using CLAS
• Cross sections and beam asymmetries for $\vev{e}p \to enπ^+$ in the nucleon resonance region for $1.7\le Q^2\le 4.5(GeV{)}^2$
• Electroexcitation of the Roper resonance in the relativistic quark models
• Quadrupole moments of baryons
• Further evidence for N(1900)P_{13} from photoproduction of hyperons
• Moments of the Spin Structure Functions g_1^p and g_1^d for 0.05 < Q^2 < 3.0 GeV^2
• Empirical transverse charge densities in the nucleon-to-P11(1440) transition
• Determination of quadrupole strengths in the gamma*p-->Delta(1232) transition at Q2= 0.20 (GeV/c)2
• Cascade production in the reactions gamma p --> K+ K+ (X) and gamma p --> K^+ K^+ pi- (X)
• Cross Sections for the $\gamma p\to K^{\ast 0}{\Sigma }^{+}$ Reaction at $E_{\gamma }=1.7-3.0$ GeV