A numerical analysis to the scalar form-factor in the ππ and KK coupled–channel system is made by solving the coupled-channel dispersive integral equations, using the iteration method. The solutions are found not unique. Physical application to the ππ central production in the pp → ppππ process is discussed based upon the numerical solutions we found. PACS numbers: 14.40.Aq; 11.55.Fv; 13.75.Lb ...

We report the results from a study of the full sample of ∼ 6.031 × 10 K → πππ decays recorded by the NA48/2 experiment at the CERN SPS. As first observed in this experiment, the ππ invariant mass (M00) distribution shows a cusp-like anomaly in the region around M00 = 2m+, where m+ is the charged pion mass. This anomaly has been interpreted as an effect due mainly to the final state charge excha...

A numerical analysis to the scalar form-factor in the ππ and KK coupled–channel system is made by solving the coupled-channel dispersive integral equations, using the iteration method. The solutions are found not unique. Physical application to the ππ central production in the pp → ppππ process is discussed based upon the numerical solutions we found. PACS numbers: 14.40.Aq; 11.55.Fv; 13.75.Lb ...

CERN measurements of πp → ππn on polarized target at 17.2 GeV/c enable experimental determination of partial wave production amplitudes below 1080 MeV. The measured S-wave transversity amplitudes provide evidence for a narrow scalar resonance σ(770). The assumption of analyticity of production amplitudes in dipion mass allows to determine S-wave helicity amplitudes S0 and S1. The helicity flip ...

The widths for ππ decay of the L = 1 charm mesons are calculated by describing the pion coupling to light constituents quarks by the lowest order chiral interaction. The wavefunctions of the charm mesons are obtained as solutions to the covariant Blankenbecler-Sugar equation. These solutions correspond to an interaction Hamiltonian modeled as the sum of a linear scalar confining and a screened ...

The dependence of KS,L → ππγ decay probabilities on photon polarization is calculated. The phases of terms of amplitude that arise from the pion-pion interaction are obtained by using a simple realistic model of pion-pion interaction via virtual ρ-meson, instead of the ChPT. The results are compared with those of other authors and the origin of the discrepancies is explained. It is shown that t...

The reaction A(π, ππ)X has been studied at low energies, paying particular attention to the interaction of the two final pions in the scalar isoscalar (I=J=0) channel. We have developed a microscopic model for the pion production , and then implemented the two pion final state interaction by using the results of a non-perturbative unitary coupled-channels method based in the standard chiral Lag...

A recent criticism raised by M.R.Pennington on our ππ-production amplitudes seems to be due to his misunderstanding on our description, and is not right. Essential point of the relation between our scattering and production amplitudes is, in connection to the unitarity and the final state interaction theorem, briefly explained. Recently, we had analyzed the ππ-scattering phase shift 2), 3) *) a...

In this study, we calculate the pressure of interacting pion gas using Beth–Uhlenbeck approach to relativistic virial expansion with Breit–Wigner phase shifts for σ- and ϱ-meson resonances. The repulsive shift δ02 is taken from quark interchange model Barnes Swanson, which in very good agreement experimental data. work show that cancellation attractive (I = 0) 2) isospin channel contributions s...

A joint analysis of the ππ and ππ S-wave amplitudes including results of three experiments has been performed. Using our theoretical model of the ππ production in which not only the pion exchange but also the a1 meson exchange were taken into account we have obtained a unique solution (called ”down-flat”) for the scalar-isoscalar phase shifts. Thus a long-standing problem of ambiguities in the ...