N* and Delta* decays into N pi0 pi0

Decays of baryon resonances in the second and the third resonance region into N pi0 pi0 are studied by photoproduction of two neutral pions off protons. Partial decay widths of N* and Delta* resonances decaying into Delta(1232) pi, N(\pi\pi)_{S}, N(1440)P_{11} pi, and N(1520)D_{13} pi are determined in a partial wave analysis of this data, and data from other reactions. Several partial decay widths were not known before. Interesting decay patterns are observed which are not even qualitatively reproduced by quark model calculations. In the second resonance region, decays into Delta(1232) pi dominate clearly. The N(\pi\pi)_{S}-wave provides a significant contribution to the cross section, especially in the third resonance region. The P_{13}(1720) properties found here are at clear variance to PDG values.Comment: 13 pages, 4 figures, long author's lis

Evidence for a parity doublet Δ(1920)P₃₃ and Δ(1940)D₃₃ from γp→pπ0η

Evidence is reported for the existence of a parity doublet of Delta resonances with total angular momentum J=3/2 from photoproduction of the p pi(0)eta final state. The two parity partners Delta(1920)P-33 and Delta(1940)D-33 make significant contributions to the reaction. Cascades of resonances into Delta(1232)eta, N(1535)pi, and Na-0(980) are clearly observed

New results on the Roper resonance and the P-11 partial wave

Properties of the Roper resonance, the first scalar excitation of the nucleon, are determined. Pole positions and residues of the P-11 partial wave are studied in a combined analysis of pion- and photo-induced reactions. We find the Roper pole at (1371 +/- 7) - i(92 +/- 10) MeV and an elasticity of 0.61 +/- 0.03. The largest decay coupling is found for the N sigma (sigma = (pi pi)-S-wave). The analysis is based on new data on gamma p -< p pi(0)pi(0) for photons in the energy range from the two-pion threshold to 820 MeV from TAPS at Mainz and from 0.4 to 1.3 GeV from Crystal Barrel at Bonn and includes further data from other experiments. The partial wave analysis excludes the possibility that the Roper resonance is split into two states with different partial decay widths