Related papers: Two pion electroproduction
We have extended a model for the $\gamma N\to \pi\pi N$ reaction to virtual photons and selected the diagrams which have a $\Delta$ in the final state. With this model we have evaluated cross sections for the virtual photon cross section as…
A model for the pion photoproduction on nuclei in the $A\left({\gamma ,\, \pi NN} \right)B$ reaction is presented. This is an extension of our recent model for the $A\left({\gamma ,\, \pi N} \right)B$ reaction. In this approach we have…
In this talk we cover several issues concerning pion production. The first one is the p p ----> p p pi^0 reaction where an alternative explanation based on the off shell extrapolation of the pi N amplitude is offered. A recent model for the…
The dynamical model developed in [Phys. Rev. C 54, 2660 (1996)] has been applied to investigate the pion electroproduction reactions on the nucleon. It is found that the model can describe to a very large extent the recent data of p(e,e'…
Reactions A(\gamma, pi^+p) are considered to proceed through the formation of pion-proton pairs on delta constituents in nuclei. We develop the nonrelativistic operator for \Delta^{++}(\gamma, pi^+)p process in an arbitrary frame. The…
The (\pi^{-}\Delta^{++}) production on the nucleon by real and virtual photons is discussed as initial step in a simple model approach for the two pion photo- and electroproduction on the nucleon, with emphasis on nucleon resonance…
We have studied the gamma d ---> Delta++ Delta- reaction which requires the collaboration of the two nucleons in deuteron. By means of a model previously developed for the gamma p ----> p pi+ pi- reaction, the two body exchange currents…
The reaction $\gamma p\to p\pi^0\eta$ has been studied with the CBELSA detector at the tagged photon beam of the Bonn electron stretcher facility. The reaction shows contributions from $\Delta^+(1232)\eta$, $N(1535)^+\pi^0$ and $pa_0(980)$…
Recent information on invariant mass distributions of the $\gamma p\to\pi^+\pi^0 n$ reaction, where previous theoretical models had shown deficiencies, have made more evident the need for new mechanisms, so far neglected or inaccurately…
The dynamical model of pion electroproduction developed by the authors has been extended to study the pion weak production reaction. The axial vector N-Delta transition form factor G_A^{N\Delta} obtained from the analysis of existing…
Radiative pion photoproduction in the $\Delta(1232)$ resonance region is studied with the aim to access the $\Delta^+(1232)$ magnetic dipole moment. We present a unitary model of the $\gamma p \to \gamma \pi N$ ($\pi N = \pi^0 p, \pi^+ n$)…
A detailed study of the elementary p(p,p$'\pi^{+}$)n reaction is presented using the delta isobar model. In this model, in the first step one of the two protons in the initial state gets excited to $\Delta $. This, in the second step,…
We describe the pion electroproduction processes in the $\Delta$(1232)-resonance region within the framework of chiral effective-field theory. By studying the observables of pion electroproduction in a next-to-leading order calculation we…
Within a dynamical coupled-channels model which has already been fixed from analyzing the data of the pi N -> pi N and gamma N -> pi N reactions, we present the predicted double pion photoproduction cross sections up to the second resonance…
We obtain the electromagnetic form factors of the $\gamma N\Delta$ transition by analyzing recent pion-electroproduction data using a fully relativistic dynamical model. Special care is taken to satisfy Ward-Takahashi identities for the…
A model for the gamma p ----> pion+ pion- p reaction developed earlier is extended to account for all isospin channels. The model includes N, Delta(1232), N^*(1440) and N^*(1520) as intermediate baryonic states and the rho-meson as an…
A review of our works providing a theoretical description of incoherent pion photoproduction on the deuteron is presented. The existing $\gamma d\to\pi NN$ data are analysed, especially those obtained more recently by the CLAS Collaboration…
A resonance model for two-pion production in the pion-nucleon reaction is developed that includes information obtained in the analysis of pion-nucleon scattering in a meson-exchange model. The baryonic resonances Delta(1232), N*(1440),…
The dynamical model of pion electroproduction has been extended to investigate the weak pion production reactions. The predicted cross sections of neutrino-induced pion production reactions are in good agreement with the existing data. We…
The study of the $\gamma^* N\rightarrow \Delta$ reaction presents the best quantitative method to explore the deviation of hadron shapes from spherical symmetry (nonspherical amplitudes). Significant non-spherical electric (E2) and Coulomb…