相关论文: Electromagnetic Couplings of Nucleon Resonances

We investigate photoproduction of eta mesons off protons and neutrons within a coupled-channels effective-Lagrangian method which is based on the K-matrix approach. The two-body final channels included are pi-N, eta-N, phi-N, rho-N,…

Electroproduction of pions on the nucleon near the threshold is analyzed within the framework of baryon chiral perturbation theory. We give a thorough discussion of the low--energy theorems related to charged and neutral…

Data on the reaction $\gamma p\to K^+\Lambda$ from the CLAS experiments are used to derive the leading multipoles, $E_{0+}$, $M_{1-}$, $E_{1+}$, and $M_{1+}$, from the production threshold to 2180\,MeV in 24 slices of the invariant mass.…

The reactions $\gamma p\to\pi^0 p$ and $\gamma p\to\pi^+ n$ are analyzed in a semi-phenomenological approach up to $E\sim2.3$ GeV. Fits to differential cross section and single and double polarization observables are performed. A good…

The role of the nucleon resonances ($N^*$) in $\omega$ photoproduction is investigated by using the resonance parameters predicted by Capstick and Roberts. The contributions from the nucleon resonances are found to be significant in various…

Data on single- and double-charged pion electroproduction off protons are successfully described in the second and third nucleon resonance regions with common N* photocouplings. The analysis was carried out using separate isobar models for…

Electrocouplings of excited proton states with masses less than 1.8 GeV were determined for the first time from the CLAS data on $\pi^+\pi^-p$ electroproduction at photon virtualities $Q^2$ $<$ 1.5 GeV$^2$. Electrocouplings were obtained…

We explore the photoproduction mechanisms for charged and neutral pion pairs off a heavy nucleus at threshold. We calculate the production of charged pairs in the Coulomb field of the nucleus in the Born approximation using explicit…

We present an optimization scheme that employs a Genetic Algorithm (GA) to determine the properties of low-lying nucleon excitations within a realistic photo-pion production model based upon an effective Lagrangian. We show that with this…

Single pi0 photoproduction has been studied with the CB-ELSA experiment at Bonn using tagged photon energies between 0.3 and 3.0 GeV. The experimental setup covers a very large solid angle of about 98% of 4 pi. Differential cross sections…

We have analysed pion photoproduction imposing constraints from fixed t dispersion relations and unitarity. Coupled integral equations for the S and P wave multipoles were derived from the dispersion relations and solved by the method of…

The two reactions $\gamma p\to K^+\Lambda$ and $\pi^-p\to K^0\Lambda$ are analyzed to determine the leading photoproduction multipoles and the pion-induced partial wave amplitudes in slices of the invariant mass. The multipoles and the…

The double pion photoproduction off nucleons near threshold is analyzed in a covariant baryon chiral perturbation theory up to next to leading order, where the $\Delta(1232)$, $N^*(1400)$ and $\rho(770)$ resonances are included as explicit…

In the present talk, we report a recent investigation on photoproduction of the $\gamma N \to f_0(500)N$ within a framework of the effective Lagrangian. We include the nucleon resonances with pin $1/2$ in the $s$ channel. The coupling…

Neutrino-induced pion and photon production from nucleons and nuclei are important for the interpretation of neutrino-oscillation experiments, and these processes are potential backgrounds in the MiniBooNE experiment [A. A. Aquilar-Arevalo…

We report on a novel scheme based on the chiral Lagrangian. It is used to analyze pion-nucleon scattering, pion photoproduction, and nucleon Compton scattering. Subthreshold partial-wave amplitudes are calculated in chiral perturbation…

We present a detailed phenomenological study of photoproduction of two hadrons, both with high transverse momentum, in longitudinally polarized lepton-nucleon collisions. We consistently include ``direct'' and ``resolved'' photon…

We present a nucleon resonance analysis by simultaneously considering all pion- and photon-induced experimental data on the final states gamma N, pi N, 2 pi N, eta N, K Lambda, K Sigma, and omega N for energies from the nucleon mass up to…

Elastic virtual photoproduction of charmonia on nucleons is calculated in a parameter free way with the light-cone dipole formalism and the same input: factorization in impact parameters, light-cone wave functions for the photons and the…

For complete development of quantum electrodynamics in the presence of a strong external field, the proper understanding of resonant processes and all their peculiarities is essential. We present our attempt to analytically investigate the…