Electromagnetic Transition Form Factors of Nucleon Resonances.

Recent measurements of nucleon resonance transition form factors with CLAS at Jefferson Lab are discussed. The new data resolve a long-standing puzzle of the nature of the Roper resonance, and confirm the assertion of the symmetric constituent quark model of the Roper as the first radial excitation of the nucleon. The data on high Q(2) n pi(+) production confirm the slow fall off of the S-11 (1535) transition form factor with Q(2), and better constrain the branching ratios beta(N pi) = 0.50 and beta(N eta) = 0.45. For the first time. the longitudinal transition amplitude to the S-11 (1535) was extracted from the n pi(+) data. Also. new results on the transition amplitudes for the D-13(1520) resonance are presented showing a rapid transition from helicity 3/2 dominance seen at the real photon point to helicty 1/2 dominance at higher Q(2).