Related papers: Counting pions in the nucleon
Nonminimal substitution terms in electroweak currents are studied in effective chiral soliton models. It is found that the terms describing the structure of the pion lead to sizable effects in form factors and polarizabilities of the…
Neutrino-induced pion production constitutes an important contribution to neutrino-nucleus scattering cross sections at intermediate energies. A deep understanding of this process is mandatory for a correct interpretation of…
We report on recent results obtained by the above collaboration on the collision processes involving three nucleons, where we pay particular attention on the dynamical role of the pion. After discussing the case at intermediate energies,…
A new theoretical framework is proposed for the description of baryon light-cone distribution amplitudes, based on the observation that their scale dependence to leading logarithmic accuracy is described by a completely integrable model.…
We have calculated coupling constants of a neutral pion with the lowest two nucleon resonances. This includes both the diagonal as well as non-diagonal coupling constants involving a nucleon resonance and a nucleon. For this, we first…
Differences among calculations of the atmospheric neutrino beam can be traced in large part to differences in the representation of pion production by protons interacting with nuclei in the atmosphere. In this paper we review the existing…
A phenomenological Dyson-Schwinger equation approach to QCD, formalised in terms of a QCD based model field theory, is used to calculate the electromagnetic charge radius of the pion. The contributions from the quark core and pion loop, as…
The experimental and theoretical status of elastic electron scattering from the nucleon is reviewed. A wealth of new data of unprecedented precision, especially at small values of the momentum transfer, in parallel to new theoretical…
Protons and neutrons are the building blocks of matter, glued together in nuclei by strong interactions. They can be excited by pions, real and virtual photons, neutrinos and other probes. These excitations are referred to as light baryon…
We review the status of baryon form factors with a special focus on the nucleon electromagnetic form factors which are known best. First, we give an introduction into the dispersive analyses and emphasize the role of unitarity and…
Three recent experiments, which looked at pionic effects in nuclei have concluded that there are no excess pions. This puts into serious question the conventional meson-exchange picture of the nucleon-nucleon interaction. Based on arguments…
There exist four pion nucleon coupling constants, $f_{\pi^0, pp}$, $-f_{\pi^0, nn}$, $f_{\pi^+, pn} /\sqrt{2}$ and $ f_{\pi^-, np} /\sqrt{2}$ which coincide when up and down quark masses are identical and the electron charge is zero. While…
We use our model for neutrino pion production on the nucleon to study pion production on a nucleus. The model is conveniently modified to include in-medium corrections and its validity is extended up to 2 GeV neutrino energies by the…
The dependence of the nucleon polarization in the reaction $e^+ + e^- \to N + \bar{N} +\pi^0 $ over different invariant variables in frame of the non-resonant mechanism, has been derived. The nucleon polarization is expressed in terms of…
A new operator for pion photo- and electroproduction has been developed for nuclear applications at photon equivalent energies up to 1 GeV. The model contains Born terms, vector mesons and nucleon resonances ($P_{33}(1232)$, $P_{11}(1440)$,…
Photoproduction of two pions on nucleon and deuteron is studied for photon energies from threshold up to $E_\gamma = 1.5$ GeV. For the elementary operator an effective Lagrangean approach is used with resonance and Born contributions. The…
The pion and nucleon mass differences generate a very pronounced cusp in the photoproduction reaction of a single neutral pion on the proton. A nonrelativistic effective field theory to describe this reaction is constructed. The approach is…
We present a detailed quark-model study of pion photoproduction within the effective Lagrangian approach. Cross sections and single-polarization observables are investigated for the four charge channels, $\gamma p\to \pi^+ n$, $\gamma n\to…
We compute pion-nucleon scattering at tree-level within a gauged linear sigma model which contains the nucleon and its chiral partner. Such an investigation in principle allows to make definite predictions as to whether the main…
The methods used in the evaluation of the neutrino-nucleus cross section are reviewed. Results are shown for a variety of targets of practical importance. Many of the described reactions are accessible in future experiments with neutrino…