相关论文: Electromagnetic Excitation of Nucleon Resonances
Form factors are Lorentz invariant functions describing the internal structure of a system. In particular, they encode how physical properties like, e.g., charge, energy, momentum, and pressure are spatially distributed. While nucleon…
We investigate theoretically a nuclear excitation mechanism involving absorption of non-resonant photons leveraged by the coupling to the atomic shell. The nuclear non-resonant photoexcitation is assisted by electron recombination which…
Electromagnetic form factors have long been used to probe the underlying charge and magnetization densities of hadrons and nuclei. Traditional three-dimensional Fourier transform methods are not rigorously applicable for systems with…
A brief overview of the recent activity in the measurement of the elastic electromagnetic proton and neutron form factors is presented. It is discussed how the quality of the data has been greatly improved by performing double polarization…
There has been much activity in the measurement of the elastic electromagnetic proton and neutron form factors in the last decade, and the quality of the data has been greatly improved by performing double polarization experiments, in…
A relativistic light-front quark model is used to describe both the elastic nucleon and nucleon-Roper transition form factors in a large Q2 range, up to 35 GeV2 for the elastic and up to 12 GeV2 for the resonance case. Relativistic…
We report results on the $\pi$-$\gamma$ transition form factor obtained within the hard scattering approach including transverse momentum effects and Sudakov corrections. The results clearly favor distribution amplitudes close to the…
We report the predictions for the 3q core contributions to the electroexcitation of the resonances Delta(1232)3/2+, N(1440)1/2+, N(1520)3/2-, N(1535)1/2-, and N(1675)5/2- on the proton obtained in the light-front relativistic quark model…
We compute electromagnetic and two-photon transition form factors of ground-state pseudoscalar mesons: $\pi,\,K,\,\eta_c,\,\eta_b$. To this end, we employ an algebraic model based upon the coupled formalism of Schwinger-Dyson and…
We investigate the modification induced on the nucleon-nucleon cross section by screening of the interaction inside nuclear matter. The interaction is described by the relativistic one boson exchange of $\sigma$, $\omega$ and $\pi$ mesons.…
We investigate the nonmonotonic behavior observed in the time-like nucleon electromagnetic form factors. Using a phenomenological extending vector meson dominance model, where the ground states $\rho$ and $\omega$ and their excited states…
We present a pion photoproduction model on the free nucleon based on an Effective Lagrangian Approach (ELA) which includes the nucleon resonances ($\Delta(1232)$, N(1440), N(1520), N(1535), $\Delta (1620)$, N(1650), and $\Delta (1700)$), in…
I give a brief overview of experimental studies of the spectrum and the structure of the excited states of the nucleon and what we learn about their internal structure. The focus is on the effort to obtain a more complete picture of the…
In treating the relativistic three-quark problem, a dressed-quark propagator parameterization is used which is compatible with recent lattice data and pion observables. Furthermore two-quark correlations are modeled as a series of quark…
The resonance strength of the two-step process of nuclear excitation by electron capture followed by $\gamma$ decay of the nucleus can be significantly increased in highly charged ions if the resonant capture proceeds via an excited…
A model for the pionic components of nuclear wave functions is obtained from light front dynamical calculations of binding energies and densities. The pionic effects are small enough to be consistent with measured nuclear di-muon production…
We investigate the sensitivity of the differential cross section, recoil nucleon polarization and the photon asymmetry to changes in the elementary amplitude, medium modifications of the resonance $(S_{11},D_{13})$ masses, as well as…
We employ a dispersion relation that allows to recover the phase of the electromagnetic form factor of the pion from its absolute value above threshold. Compared to alternative approaches building on the phase, this approach builds on…
In this talk, the electromagnetic transition form factors from the nucleon ground state to twelve $N^*$ and $\Delta$ states are exhibited and discussed. Those results are extracted through a comprehensive coupled-channel approach -- the…
Photoproduction of $\eta$ mesons off $^{12}$C, $^{40}$Ca, $^{93}$Nb, and $^{nat}$Pb nuclei has been measured with a tagged photon beam with energies between 0.6 and 2.2 GeV. The experiment was performed at the Bonn ELSA accelerator with the…