Consistency checks of pion-pion scattering data and chiral dispersive calculations

Photon-photon scattering, pion polarizability, and chiral symmetry.

Recent attempts to detect the pion polarizability via analysis of γγ → ππ measurements are examined. The connection between calculations based on dispersion relations and on chiral perturbation theory is established by matching the low energy chiral amplitude with that given by a full dispersive treatment. Using the values for the polarizability required by chiral symmetry, predicted and experi...

Analysis of the pion–kaon sigma–term and related topics

We calculate the one–loop contributions to the difference ∆πK between the isoscalar on–shell pion–kaon scattering amplitude at the Cheng–Dashen point and the scalar form factor ΓK(2M 2 π) in the framework of three flavor chiral perturbation theory. These corrections turn out to be small. This is further sharpened by treating the kaons as heavy fields (two flavor chiral perturbation theory). We ...

The pion-pion scattering amplitude

We obtain reliable ππ scattering amplitudes consistent with experimental data, both at low and high energies, and fulfilling appropriate analyticity properties. We do this by first fitting experimental low energy (s ≤ 1.42GeV) phase shifts and inelasticities with expressions that incorporate analyticity and unitarity. In particular, for the S wave with isospin 0, we discuss in detail several se...

Consistency of the chiral pion-pion scattering amplitudes with axiomatic constraints.

Compton scattering by pion : there is no room for the off – shell effects

Compton scattering by pion: there is no room for the off–shell effects. Abstract We show that the off–shell contributions in Compton scattering by pion may exist only in the single exchange diagrams. These contributions are canceled completely in the total gauge–invariant amplitude as it confirmed by one–loop calculations. It explains, in particular, some results of the chiral pertubation theor...