[en] The statistical system of pions with zero total isospin is studied. The suppression effects for the average yields due to isospin conservation are the same for π⁰, π⁺, and π^-. However, a behavior of the corresponding particle number fluctuations are different. For neutral pions there is the enhancement of the fluctuations, whereas for charged pions the isospin conservation suppresses fluctuations. The correlations between the numbers of charged and neutral pions are observed for finite systems. This causes a maximum of the total pion number fluctuations for small systems. The thermodynamic limit values for the scaled variances of neutral and charged pions are calculated. The enhancements of the fluctuations due to Bose statistics are found and discussed.

No abstract available

[en] The NA49 experiment at CERN SPS has acquired a huge data set of Pb + Pb events over a broad range of energy and centrality during the last several years. This high statistics data set, coupled with a state-of-the-art analysis technique, allows for the first model-independent extraction and energy scan of 3D emission sources for pion pairs at SPS energies. These 3D pion emission sources provide new insights into the nature of a long-range source previously reported by PHENIX at RHIC. Preliminary results indicate that the pion source function is essentially Gaussian from 20 A GeV to 80 A GeV but it displays significant non-Gaussian tails at 158 A GeV. (author)

No abstract available

[en] The neutral-charged pions correlation is studied following the idea of vector resonances production. A relation between the average number of neutrals as a function of negatives < n⁰>sub(n) and the multiplicity distribution of negatives is obtained and compared with recent data. (author)

No abstract available

[en] We address the problem of pion production in low-energy π-nucleus collisions. For the production mechanism, we assume a simple model consisting of a coherent sum of single pion exchange and the excitation emdash followed by the decay into two pions and a nucleon emdash of the N^*(1440) resonance. The production amplitude is modified by the final state interaction between the pions calculated using the chirally improved Juelich meson exchange model including the polarization of the nuclear medium by the pions. The model reproduces well the experimentally observed πA→ππA cross sections, especially the enhancement with increasing A of the π⁺π^- mass distribution in the threshold region. copyright 1999 The American Physical Society

[en] Pionic hydrogen is a short-lived exotic hydrogen isotope in which a negative pion replaces the atomic electron. The formation and subsequent interactions of pionic hydrogen are discussed, with emphasis on the process of pion transfer. Recent results using the pion charge-exchange reaction (π^-, π⁰) obtained at TRIUMF are reviewed. (Author) (35 refs., 3 tabs., 9 figs.)

[en] Some simple analyticity bounds involving the pion electromagnetic polarizabilities and threshold values of the (properly normalized) I = 0, 2ππ→γγ d-wave amplitudes are derived and discussed. (author)

[en] Our recent studies of a scalar resonance below 1 GeV are presented for the production processes and for the scattering process. We have observed a scalar state with a mass below 1 GeV in the π⁰π⁰ system obtained by the GAMS collaboration. We have also observed a low-mass scalar state in our analysis of the π⁺π^- system produced in the reaction J/Ψ→ωπ⁺π^- studied in the DM2 experiment. It is important to observe a low-mass scalar resonance in ππ scattering below 1 GeV. A scalar resonance with a mass around 600 MeV has been observed in our analysis of data on the S-wave ππ scattering phase shift. It can be identified with the σ particle, which has long been expected to be found as a chiral partner of the pion appearing to be a Nambu-Goldstone boson