A new evaluation of the universal ππ scattering length relation is used to extract the ππ s-wave scattering lengths from threshold pion production data. Previous work has shown that the chiral perturbation series relating threshold pion production to ππ scattering lengths appears to converge well only for the isospin-2 case, giving a2 = −0.031±0.007m−1 π . A model-independent and data-insensiti...

We perform a dispersive theoretical study of the reaction γγ → ππ emphasizing the low energy region. The large source of theoretical uncertainty to calculate the γγ → ππ total cross section for √ s & 0.5 GeV within the dispersive approach is removed. This is accomplished by taking one more subtraction in the dispersion relations, where the extra subtraction constant is fixed by considering new ...

We perform a dispersive theoretical study of the reaction γγ → ππ emphasizing the low energy region. The large source of theoretical uncertainty to calculate the γγ → ππ total cross section for √ s & 0.5 GeV within the dispersive approach is removed. This is accomplished by taking one more subtraction in the dispersion relations, where the extra subtraction constant is fixed by considering new ...

The recent experimental data of both ππ/Kπ scattering and production processes, suggesting the existence of scalar σ and κ mesons, are reviewed. In many ππ/Kπ production processes the direct effects of their productions are observed, while they are, because of chiral symmetry, hidden in scattering processes, and now σ(500∼600) and κ(800∼900) are considered to be confirmed experimentally. The re...

We demonstrate that, together with the available experimental information , chiral symmetry determines the low energy behaviour of the ππ scattering amplitude to within very small uncertainties. In particular, the threshold parameters of the S–, P –, D– and F –waves are predicted, as well as the mass and width of the ρ and of the broad bump in the S–wave. The implications for the coupling const...

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...

We present estimates of the charming penguin contribution to B → Kπ, ππ,Kη,Kη decays due to intermediate charmed meson states. We find that this contribution is indeed significant for B → Kπ decays, and its inclusion, together with the tree and penguin terms, produces large branching ratios in agreement with data, though the analysis is affected by large theoretical uncertainties. On the other ...

We discuss strategies to determine hadronic decay couplings from lattice studies. As an application, we explore the decay of a vector meson to two pseudoscalar mesons with Nf = 2 flavours of sea quark. Although we are working with quark masses that do not allow a physical decay, we show how the transition rate can be evaluated from the amplitude for ρ→ ππ and from the annihilation component of ...