Related papers: S-Wave Pion-Pion Correlations in Dense Nuclear Mat…
Extensive data on strong interaction effects in pionic atoms are analyzed with a density-dependent isovector scattering amplitude suggested recently by Weise to result from a density dependence of the pion decay constant. Most of the…
Soft-pion theorems are used to show how chiral symmetry constrains the contributions of low-momentum pions to the quark condensate, the pion decay constant and hadron masses, all of which have been proposed as signals of partial restoration…
A new analysis of S-wave production amplitudes for the reaction $\pi^- p_{\uparrow} \rightarrow \pi^+ \pi^- n$ on a transversely polarized target is performed. It is based on the results obtained by the CERN-Cracow -Munich collaboration in…
We develop a relativistic covariant and unitary description of the pion-nucleon interaction in a hadron-exchange model. The model is based on the solution of a dimensionally reduced (quasipotential) Bethe-Salpeter equation for the…
Near threshold pion production experiments have been recently carried out and used to extract S--wave $\pi\pi$ scattering lengths. We emphasize here that at present these processes are related only at the tree level (and its first…
The weak decays of hyperons and hypernuclei are studied from the chiral symmetry viewpoint. The soft pion relations are useful in understanding the isospin properties of the weak hyperon decays. Recent development on the short-range part of…
We propose a model for $D^+ \to \pi^+ \pi^- \pi^+$ decays following experimental results which indicate that the two-pion interaction in the $S$-wave is dominated by the scalar resonances $f_0(600)/\sigma$ and $f_0(980)$. The weak decay…
Differential cross sections for elastic scattering of 21.5 MeV positive and negative pions by Si, Ca, Ni and Zr have been measured as part of a study of the pion-nucleus potential across threshold. The `anomalous' repulsion in the s-wave…
Conditions are found, at which in nuclear matter there may appear a spatially nonuniform $p$ wave $\pi^0$ condensate supplemented by a spatially varying spontaneous magnetization. The pion-nucleon interaction and the anomaly contributions…
Results on the pion freeze-out phase-space density in sulphur-nucleus, Pb-Pb and pion-proton collisions at CERN-SPS are presented. All heavy-ion reactions are consistent with the thermal Bose-Einstein distrtibution f=1/(exp(E/T)-1) at T~120…
Results on the pion phase-space density at freeze-out in sulphur-nucleus, Pb-Pb and pi-p collisions at the CERN SPS are presented. All heavy-ion reactions are consistent with the thermal Bose-Einstein distribution f=1/[exp(E/T)-1] at T ~…
The present status of the in-medium invariant $\pi-\pi$ mass distribution in the sigma-meson channel around the threshold is reviewed from the theory side and contrasted with recent experiments on $(\pi,2\pi)$ knock-out reactions. A…
Recent analyses of low-energy pion-nucleon experimental data have provided clear evidence for the violation of the isospin symmetry of the strong interaction. In the present work, it is shown that the single-charge-exchange reaction is the…
The longest-range part of the nuclear force due to the one-pion exchange governs the energy dependence of the scattering amplitude in the near-threshold region and imposes correlations between the coefficients in the effective range…
We analyze Pion Nucleon Scattering up to 700 MeV using a simple, relativistic, unitary model\cite{1}. The kernel of the integral equation includes nucleon, roper, delta, D_13 as well as S_11 poles with their corresponding crossed pole terms…
We present a few simple observations on the occurrence of $\pi$-condensation in Nuclei, aimed at clarifying the nature of the $\pi$-condensation implied by the coherent nuclear $\pi$-N-$\Delta$ interaction, proposed in 1990 to explain the…
The pion-pion scattering amplitudes provided by second-order chiral perturbation theory are confronted with known rigorous constraints derived from the axioms of quantum field theory. We mainly test constraints restricting the…
We investigate the behaviour of the nuclear forces as a function of the light quark masses (or, equivalently, pion mass) in the framework of chiral effective field theory at next-to-leading order. The nucleon-nucleon force is described in…
We analyze the spin-orbit coupling term in the nuclear energy density functional in terms of a zero-range NN-contact interaction and finite-range contributions from two-pion exchange. We show that the strength of the spin-orbit contact…
We have developed a model for the N N --> N N pi pi reaction and evaluated cross sections for the different charged channels. The low energy part of those channels where the pions can be in an isospin zero state is dominated by N*…