Related papers: Interacting pion pairs in nuclear matter
We present the results of the experimental study of the reaction of dipion production by the beam of the negative pions with momentum 1.78 GeV/c on the polarized proton and liquid hydrogen targets. The experiment covers the region of dipion…
We review the cross sections for low-energy $\pi^- \gamma$ reactions in the framework of chiral perturbation theory. Charged pion Compton scattering, $\pi^- \gamma\to \pi^-\gamma$, is considered up to one-loop order where the pion's…
The subtle differences between positive and negative pion spectra can used be used to study the nature of the nuclear interaction region in heavy-ion collisions. Several large acceptance heavy ion experiments at facilities ranging from SIS,…
The near-threshold pion-induced $\phi$ production off nuclei has been studied in the kinematical conditions of the HADES experiment using a collision model based on the nuclear spectral function. Starting from the elementary reaction…
New data are presented on the p(e,e'p)\pi^0 reaction at threshold at a four-momentum transfer of Q^2=0.05 GeV^2/c^2. The data were taken with the three-spectrometer setup of the A1 Collaboration at the Mainz Microtron MAMI. The complete…
An exploratory study of chiral four-nucleon interactions in nuclear and neutron matter is performed. The leading-order terms arising from pion-exchange in combination with the chiral $4\pi$-vertex and the chiral NN$3\pi$-vertex are found to…
A theoretical analysis of the $(\pi^-,\gamma\gamma)$ reaction in nuclei is made in order to find the viability of this reaction to test modifications of the $\sigma$ meson mass in nuclear matter. The $\pi\pi$ correlation in the…
We analyze $J/\psi-$ production in nucleon-nucleon collisions near threshold in the framework of a general model independent formalism, which can be applied to any reaction $N+N\to N+N+V^0$, where $V^0=\omega$, $\phi$, or $J/\psi$. Such…
We investigate neutrino induced one pion production on nucleons. The elementary neutrino--nucleon cross section is calculated as the sum of the leading Delta pole diagram and several background diagrams obtained within the non-linear sigma…
The tagged quasi-free $np \to np\pi^+\pi^-$ reaction has been studied experimentally with the High Acceptance Di-Electron Spectrometer (HADES) at GSI at a deuteron incident beam energy of 1.25 GeV/nucleon ($\sqrt s \sim$ 2.42 GeV/c for the…
A nonrelativistic effective theory to describe the electroproduction reaction of a single pion on the nucleon at leading order in the electromagnetic coupling is constructed. The framework is tailored to accurately describe the cusp…
We compare our pion production results with recent MiniBooNE data measured in mineral oil. Our total cross sections lie below experimental data for neutrino energies above 1 GeV. Differential cross sections show our model produces too few…
We discuss two processes, the $\pi N \to e^+e^- N$ and the $\gamma N \to e^+e^- N$ reactions, below and close to the vector meson production threshold ($1.40<\sqrt s <1.75$ GeV). The aim is to gain understanding of the coupling of vector…
We examine the axion emission from supernovae with a complete set of relevant axion couplings including the axion-pion-nucleon contact interaction which was ignored in the previous studies. Two processes are affected by the…
We examine the role of the elementary isoscalar pion--nucleon scattering amplitude in the description of the processes $pp \to pp\pi^0$ and $pp\to d\pi^+$ at threshold. We argue that the presently used tree level dimension two approximation…
Carried out in this study is an improved analysis of the measurements of the three pion-nucleon ($\pi N$) reactions, which can be subjected to experimental investigation at low energy (pion laboratory kinetic energy $T \leq 100$ MeV), i.e.,…
The study of the charge asymmetry of produced particles allows to investigate the interference of different production mechanisms and to determine new features of the corresponding amplitudes. In the process $e^- e^+ \to e^- e^+ \pi^+…
Dielectron production in reactions $\pi^- p \rightarrow n e^+e^-$ and $\pi^- p \rightarrow n e^+e^- \gamma$ at energies less than 1 GeV is studied assuming electron-positron pair production to occur in the virtual time-like photon splitting…
We report calculations for exclusive pion photoproduction on nuclei beyond the first resonance region in the distorted wave impulse approximation. The elementary operator contains contributions from the resonances $P_{33}(1232)$,…
The near-threshold n p -> d pi0 cross section is calculated in chiral perturbation theory to next-to-leading order in the expansion parameter sqrt{M m_pi}/Lambda_chi. At this order irreducible pion loops contribute to the relevant…