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We present a dispersive representation of the $gamma Nrightarrow pi N$ partial-wave amplitude based on unitarity and analyticity. In this representation, the right-hand-cut contribution responsible for $pi N$ final-state-interaction effect are taken into account via an Omnes formalism with elastic $pi N$ phase shifts as inputs, while the left-hand-cut contribution is estimated by invoking chiral perturbation theory. Numerical fits are performed in order to pin down the involved subtraction constants. It is found that good fit quality can be achieved with only one free parameter and the experimental data of the multipole amplitude $E_{0}^+$ in the energy region below the $Delta(1232)$ are well described. Furthermore, we extend the $gamma Nrightarrow pi N$ partial-wave amplitude to the second Riemann sheet so as to extract the couplings of the $N^ast(890)$. The modulus of the residue of the multipole amplitude $E_{0}^+$ ($S_{11pE}$) is $2.41rm{mfmcdot GeV^2}$ and the partial width of $N^*(890)togamma N$ at the pole is about $0.369 {rm MeV}$, which is almost the same as the one of $N^*(1535)$, indicating that $N^ast(890)$ strongly couples to $pi N$ system.
We use a dispersion representation based on unitarity and analyticity to study the low energy $gamma^* Nrightarrow pi N$ process in the $S_{11}$ channel. Final state interactions among the $pi N$ system are critical to this analysis. The left-hand pa
Low-energy partial-wave $pi N$ scattering data is reexamined with the help of the production representation of partial-wave $S$ matrix, where branch cuts and poles are thoroughly under consideration. The left-hand cut contribution to the phase shift
The production of eta mesons in photon- and hadron-induced reactions has been revisited in view of the recent additions of high-precision data to the world data base. Based on an effective Lagrangian approach, we have performed a combined analysis of
The experimental data on pi N scattering in the elastic energy region T_pi < 250 MeV are analyzed within the multichannel K-matrix approach with effective Lagrangians. Isospin invariance is not assumed in this analysis and the physical values for mas
The $(n,gamma f)$ process is reviewed in light of modern nuclear reaction calculations in both slow and fast neutron-induced fission reactions on $^{235}$U and $^{239}$Pu. Observed fluctuations of the average prompt fission neutron multiplicity and a