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The AN -+ gN and gN~gN partial-wave T matrices for the eight lowest partial waves have been obtained in a three-coupled-channel model with unitarity manifestly imposed. The two physical channels are AN and gN, and the third channel, vr7rN, is an effective, but unphysical two-body channel which represents all remaining processes. The 7tN elastic phase shifts and the weighted data base of the mN~gN total and differential cross sections are chosen as the input for the fitting procedure. A model containing a single resonance in each of the three partial waves that dominates the g production at lower energies is compared with previous analyses, based on similar assumptions.A multiresonance coupled-channel model is introduced which significantly improves the agreement with all input data. Our results are compared with a complementary multiresonance coupled-channel analysis that is constrained with elastic and continuum production channels. The inclusion of the fourth Pqq resonance in the 1440 -2200 MeV region further improves the agreement between the analysis and the data. PACS number(s): 25.40.Ve, 13.75.Gx, 14.40. Aq, 24. 10.Eq

The total cross section for the near threshold η production in proton-proton collisions has been investigated with the assumption that the production mechanism is due to the emission of a meson x(π, η, σ) from one of the nucleons followed by a xN → ηN transition on the second one. The xN → ηN amplitudes are generated from the unitary multi-channel multi-resonance model which has recently been constructed in analyzing the πN scattering and πN → ηN reaction. The initial and final pp distortions are calculated from a coupled-channel πN N model which describes the N N scattering data up to about 2 GeV. With the x − N N vertex functions taken from the Bonn potential, the predicted total cross sections of threshold pp → ηpp reaction are in good agreement with the data. In contrast to previous works, we find that the η-exchange plays an important role. The effect of the two-pion exchange, simulated by σ-exchange, is found to be significant but not as dominant as the vector meson-exchange introduced in previous works.The η production in proton-proton collisions has attracted a lot of interest in the past decade. A theoretical understanding of this two-nucleon process near the production threshold is needed for exploring the N * (S 11 (1535)) dy-

We present a new approach to quantifying pole parameters of single-channel processes based on a Laurent expansion of partial-wave T-matrices in the vicinity of the real axis. Instead of using the conventional power-series description of the non-singular part of the Laurent expansion, we represent this part by a convergent series of Pietarinen functions. As the analytic structure of the non-singular part is usually very well known (physical cuts with branch points at inelastic thresholds, and unphysical cuts in the negative energy plane), we find that one Pietarinen series per cut represents the analytic structure fairly reliably. The number of terms in each Pietarinen series is determined by the quality of the fit. The method is tested in two ways: on a toy model constructed from two known poles, various background terms, and two physical cuts, and on several sets of realistic πN elastic energy-dependent partial-wave amplitudes (GWU/SAID -[1, 2], and Dubna-Mainz-Taipei - [3,4]). We show that the method is robust and confident using up to three Pietarinen series, and is particularly convenient in fits to amplitudes, such as single-energy solutions, coming more directly from experiment; cases where the analytic structure of the regular part is apriori unknown.