We propose an intensity-dependent pion-nucleon coupling Hamiltonian within a unitary multiparticle-production model of the Auerbach-Avin-Blankenbecler-Sugar (AABS) type in which the pion field is represented by the thermal-density matrix. Using this Hamiltonian, we explain the appearance of the negative-binomial (NB) distribution for pions and the well-known empirical relation, the so-called Wr...

γγ → Π0t is the major production mechanism of neutral top-pion at the linear colliders. In this paper, we calculate the cross section of the process γγ → Π0t and discuss the potential to observe the neutral top-pion via its various decay modes at the planned ILC. The study show that, among the various neutral top-pion production processes at the linear colliders, the cross section of γγ → Π0t i...

Recent developments and open issues in chiral dynamics with strange quarks are reviewed. Topics include: Order parameters of chiral symmetry breaking, the flavor dependence of these order parameters, speculations about the phase structure of QCD with varying number of flavors, OZI violation and its natural emergence in case of a small strange quark condensate, heavy kaon chiral perturbation the...

We develop a relativistic quark model for pion structure, which incorporates the non-trivial structure of the vacuum of Quantum Chromodynamics as modelled by instantons. Pions are boundstates of quarks and the strong quark-pion vertex is determined from an instanton induced effective lagrangian. The interaction of the constituents of the pion with the external electromagnetic field is introduce...

The structure of the ππ interaction at low energies is strongly constrained by the fact that the pion is the Goldstone boson of a spontaneously broken approximate symmetry of QCD.1 The scattering amplitude can be calculated in a systematic way in the framework of Chiral Perturbation Theory (ChPT),2 by an expansion which converges very rapidly near the center of the Mandelstam triangle. However,...

The scattering lengths of a two pion system are the golden magnitudes to test the QCD predictions in the low energy sector. The DIRAC (PS-212) experiment at CERN will obtain a particular combination of the S-wave isospin 0 and 2 scattering lengths by measuring the lifetime of pionium, the hydrogen-like π+π− atom. This measurement tests the accurate predictions of the Chiral Perturbation Theory....

We investigate a domain-structured source in the pion interferometry of relativistic nuclear collisions. The source emits coherent pions intermittently with the background of chaotic pions. The coherent pions examined are either of a general nature or of disoriented chiral condensate. Twoand three-pion correlations for the source are shown to agree well with the recent NA44 experimental data. P...

We have extended a model for the γN → ππN reaction to virtual photons and selected the diagrams which have a ∆ in the final state. The agreement found with the γ v p → ∆ 0 π + and γ v p → ∆ ++ π − reactions is good. The sensitivity of the results to N ∆ transition form factors is also studied. The present reaction, selecting a particular final state, is an extra test for models of the γ v N → π...

Based on a prior model on double pion photoproduction on the proton, successfully tested in total cross sections and invariant mass distributions, we make a theoretical study of the angular dependence of helicity asymmetries from the interaction of circularly polarized photons with unpolarized protons. We show that this observable is sensitive to details of the internal mechanisms and, thus, re...