Constraints on low energy QCD parameters from $$\eta \rightarrow 3\pi $$ η → 3 π and $$\pi \pi $$ π π scattering

Π-η Mixing from Qcd Sum Rules

The q2 dependence of the π-η mixing amplitude is examined with the use of QCD sum rules. The linear slope of the mixing function θ(q2) is found to be much smaller than that for ρ-ω mixing. Thus the mixing amplitude is approximately the same in the space-like region as in the time-like one, and one may neglect the q2 dependence of the mixing. A comparison between a hadron-meson, an effective chi...

Se p 20 07 Physics of η ′ → π + π − η and η ′ → π + π − π 0 decays

The article describes experimental status of the η ′ → π+π−η and η ′ → π+π−π0 decays. A theoretical framework used for description of the decays mechanism is also reviewed. The possibilities for the measurements with WASA-at-COSY are mentioned.

η → π + π − π 0 γ in Chiral Perturbation Theory

γγ → π 0 π 0 and η → π 0 γγ at low energy within the Extended Nambu Jona - Lasinio Model ∗

Parameters and Application to Π 0 , Η , Η ′

The chiral expansion of the low energy processes π 0 → γγ and η → γγ is reconsidered with particular emphasis on the question of the evaluation of the two low-energy parameters from L W Z (6) which are involved at chiral order six. It is shown how extensive use of sum-rules and saturation with resonances as well as constraints from asymptotic QCD effectively determine their values. Predictions ...