  The nucleon resonances are investigated within a dynamical coupled-channels
model of pi N and gamma N reactions up to the invariant mass W = 2 GeV. The
meson-baryon (MB) channels included in the calculations are MB = pi N, eta N, K
Lambda, K Sigma, and pi pi N that has pi Delta, rho N, and sigma N resonant
components. The meson-baryon amplitudes T_{M'B',MB}(W) are calculated from
solving a set of coupled-channels integral equations defined by an interaction
Hamiltonian consisting of (a) meson-exchange interactions v_{M'B',MB} derived
from phenomenological Lagrangian, and (b) vertex interactions N* --> MB for
describing the transition of a bare excited nucleon state N* to a channel MB.
The parameters of v_{M'B',MB} are mainly constrained by the fit to the data of
pi N --> pi N in the low energy region up to W =1.4 GeV. The bare masses of N*
and the N* --> MB parameters are then determined in simultaneous fits to the
data of pi N --> pi N up to W =2.3 GeV and those of pi N --> eta N, K Lambda, K
Sigma and gamma N --> pi N, eta N, K Lambda, K Sigma up to W = 2.1 GeV. The
pole positions and residues of nucleon resonances are extracted by analytically
continuing the meson-baryon amplitudes T_{M'B',MB}(W) to the complex Riemann
energy surface. From the extracted residues, we have determined the N* --> pi
N, gamma N, eta N, K Lambda, K Sigma transition amplitudes at resonance poles.
We compare the resonance pole positions from our analysis with those given by
Particle Data Group and the recent coupled-channels analyses by the Juelich and
Bonn-Gatchina groups. Four results agree well only for the first N* in each
spin-parity-isospin (J^P,I) channel. For higher mass states, the number of
states and their resonance positions from four results do not agree well. We
discuss the possible sources of the discrepancies and the need of additional
data from new hadron facilities such as J-PARC.
