A correct understanding and description of the I = 2 ππ S-wave interaction is important for the extraction of the I = 0 ππ S-wave interaction from experimental data and for understanding the I = 0 ππ S-wave interaction theoretically. With t-channel ρ, f 2 (1270) exchange and the ππ → ρρ → ππ box diagram contribution, we reproduce the ππ isotensor S-wave and D-wave scattering phase shifts and in...

A general prescription for the construction of ππ interaction potentials which preserve scattering length constraints from chiral symmetry when iterated in scattering equations is derived. The prescription involves only minor modifications of typical meson-exchange models, so that coupling constants and cutoff masses in the models are not greatly affected. Calculations of s-wave ππ scattering a...

The Schrödinger equation discribing the local potential model of a strong ππ-interaction was studied. The influence of the strong ππ-interaction of the behaviour of pionium nS-state wave functions at small distances is studied both analytically (perturbatively) and numerically. It is shown that in the whole the accounting of strong interaction results in multiplying pure Coulomb pionium wave fu...

A meson exchange model of the ππ interaction which fits free ππ scattering data is used to calculate the interactions of pions in nuclear matter as a function of nuclear density. Polarization of the nuclear medium by the pions results in a marked increase in the s-wave ππ attraction at low energy. The influence of this effect on the nucleon-nucleon interaction is a corresponding increase with d...

The phases of terms of amplitude that arise from the ππ interaction are obtained by using a simple realistic model of ππ interaction via virtual ρ-meson, instead of the ChPT. It is shown that the standard ChPT approach cannot reproduce the contribution of the ρ-meson to the ππ interaction. It is shown that the interference between the terms of amplitude with different CP-parity appears only whe...

With t-channel ρ, f 2 (1270) exchange and the ππ → ρρ → ππ box diagram contribution, we reproduce the ππ isotensor S-wave and D-wave scattering phase shifts and inelasticities up to 2.2 GeV quite well in a K-matrix formalism. The t-channel ρ exchange provides repulsive negative phase shifts while the t-channel f 2 (1270) gives an attractive force to increase the phase shifts for ππ scattering a...

Two sources of strong phases in the decays B to ππ are identified: (1) “quasi-elastic scattering” corresponding to intermediate states like ππ and ρρ, (2) “cc̄” corresponding to intermediate states like DD̄ and D∗D̄∗. Possibilities of using data to identify these two sources are discussed and illustrated. Present data suggests both sources may be significant. The decay of B → ππ may be considered ...

π + π − e ± ν (Ke4) decay. Thanks to the absence of other hadrons in the final state the ππ interaction can be analyzed in terms of phase shift variation with the ππ invariant mass. The preliminary results on a set of ∼ 1150000 K events collected in two years of data taking, will be discussed. The second way to evaluate the ππ scattering lengths is based on the accurate study of K → πππ Dalitz ...

Electromagnetic corrections to the low-energy π+π− → π0π0 scattering amplitude at next-to-leading order in the chiral expansion are reviewed. Their effects on the corresponding scattering lengths are estimated and compared to the two-loop strong interaction contributions. Key-Words: Chiral perturbation theory, Pion, Electromagnetic corrections. Contribution to the Eighth International Symposium...