相关论文: Isoscalar off-shell effects in threshold pion prod…
A brief overview on recent model calculations for near threshold pion production in nucleon-nucleon collisions is given. Results from our own investigations of the reactions $pp \rightarrow pp\pi ^0$ and $pn \rightarrow d\pi^0$ are…
A model calculation for pion production in nucleon-nucleon collisions is presented. Direct production, pion rescattering and contributions from pair diagrams are taken into account. The amplitudes for the elementary processes are based on…
We present the contributions of the non-linear chiral scalar field S to cross sections of $pp\to d\pi ^{+}, pp\to pn\pi ^{+}$ and $pp\to pp\pi ^0$ reactions at threshold. We compare our results with the meson $\sigma$ contribution from the…
The production near threshold of isoscalar pion pairs in the pd -> 3He(pi pi)^0 reaction is estimated in a two-step model which successfully describes the production of eta, omega and eta' mesons. A virtual pion beam, generated through an…
The large variety of experimental data around the pion-production threshold are compared with a meson-exchange isobar model which includes the pion-nucleon interaction in s-- and p-waves. Theoretical results obtained with two different NN…
We have calculated the proton analyzing power A_{y0} of the pion-production reaction from pd collisions for one energy close to threshold and for another in the region of the $\Delta$-resonance. A fair reproduction of the experimental data…
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…
We address the problem of pion production in low energy $\pi$-nucleus collisions. For the production mechanism we assume a simple model consisting of a coherent sum of single pion exchange and the excitation---followed by the decay into two…
We present an analysis of isospin-breaking effects in threshold pion-nucleon scattering due to the light quark mass difference and the dominant virtual photon effects. We discuss the deviation from various relations, which are exact in the…
Pion electro- and photoproduction off the nucleon close to threshold is studied in covariant baryon chiral perturbation theory at O($p^3$) in the extended-on-mass-shell scheme, with the explicit inclusion of the $\Delta(1232)$ resonance.…
Pion production at threshold from nucleon-deuteron collisions is considered, with reference to the outgoing channel where the three-nucleon system is bound. The available experimental data are compared with calculations using accurate…
We investigate isospin breaking in low-energy pion-nucleon scattering in the framework of chiral perturbation theory. This work extends the systematic analysis of [1] to the energy range above threshold. Various relations, which identically…
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…
Positive pion electroproduction from the deuteron near threshold has been considered within an approach based on the unitary transformation method. The gauge independence of the treatment is provided by using an explicitly gauge independent…
The spin and isospin structure of the amplitudes and observables for K+Lambda production in nucleon-nucleon collisions in the near-threshold region is analysed. It is shown that, with reasonable values for the relative strengths of the pi…
The first data from MAX-lab in Lund, Sweden on pion production in photonuclear reactions at threshold energies, is presented. The decrease of the total yield of pi+ in gamma + 12C, 27Al reactions below 200 MeV as well as differential,…
Estimation of the back-to-back pi-pi correlations arising due to evolution of the pionic field in the course of pion production process is given for central heavy nucleus collisions at moderate energies.
The pion-production $\pi^+ A \to \pi^+\pi^{\pm} A'$ reactions were studied on nuclei $^{2}H$, $^{12}C$, $^{40}Ca$ and $^{208}Pb$ at a pion energy of $T_{\pi^{+}}$=283 MeV using the CHAOS spectrometer. The experimental results are reduced to…
We investigate the observable effects of off-shell propagation of nucleons in heavy-ion collisions at SIS energies. Within a semi-classical BUU transport model we find a strong enhancement of subthreshold particle production when off-shell…
Off-shell propagation of nucleons is neglected in one-body transport models of heavy-ion collisions, but it could be significant in processes that are limited by phase space, such as the threshold production of heavy particles. We estimate…