[en] The scalar meson exchange in θ → P⁰P⁰γ decay is discussed in a chiral invariant framework where the scalar meson poles are incorporated explicitly. θ → π⁰π⁰γ and θ → π⁰ηγ are in agreement with recent experimental data and can be used to extract valuable information on the properties of f₀(980) and a₀(980) respectively. θ → K⁰K⁰γ is shown not to pose a background problem for testing CP violation at Daθne. The ratio θ → f₀γ/a₀γ is also predicted

[en] The complementarity between Chiral Perturbation Theory and the Linear Sigma Model is exploited to study scalar meson exchange in V → P⁰P⁰γ decays. The recently reported experimental data on phi → π⁰π⁰γ, phi → π⁰ηγ and ρ → π⁰π⁰γ can be satisfactorily accommodated in our framework

[en] The scalar contributions to the radiative decay φ→K⁰ anti K⁰γ are studied within the framework of the Linear Sigma Model (LσM). Theoretical predictions for the associated subprocesses φ→f₀γ and φ→a₀ γ as well as the ratio φ→f₀ γ/a₀γ are also given. (orig.)

[en] An analysis of various radiative VPγ decays is performed using the two mixing angle description of the η-η^' system. The agreement is excellent. Our results are expressed both in the 'octet-singlet' and in the 'quark-flavour' basis. It turns out that at the present experimental accuracy, the two angles are significantly different in the former, but not in the latter basis

[en] A phenomenological analysis of various decay processes is performed in order to test the large N_c Chiral Perturbation Theory predictions for the octet and singlet pseudoscalar decay constants and mixing angles. The results obtained hint at a disagreement with the expectations of this theoretical framework although the statistical significance is still limited. (author)

[en] The η - η' pseudoscalar mixing angle and the gluonium content of the η' meson are deduced from an updated phenomenological analysis of V → Pγ and J/ψ → V P decays. In absence of gluonium, the value of the mixing angle in the quark-flavour basis is found to be φ_P = (41.5 ± 1.2)^o from V → Pγ and φ_P = (40.5 ± 2.4)^o from J/ψ → V P. In presence of gluonium, the values for the mixing angle and the gluonic content of the η' wave function are φ_P = (41.4 ± 1.3)^o and Z²_η' = 0.04 ± 0.09 from V → P γ and φ_P = (44.5 ± 4.3)^o and Z²_η' = 0.28 ± 0.21 from J/ψ → V P, respectively. (author)

[en] The η-η' mixing angle is deduced from an updated phenomenological analysis of J/ψ decays into a vector and a pseudoscalar meson. Its value in the quark-flavour basis is found to be φ_P (40.5±2.4)⁰, in agreement with most recent analyses. Corrections due to non-ideal ω-φ mixing are shown to be negligible. The newly reported values of B(J/ψ→ρπ) by the BABAR and BES Collaborations are crucial to get a consistent description of data

[en] The η-η' pseudoscalar mixing angle and the gluonium content of the η' meson are deduced from an updated phenomenological analysis of J/ψ decays into a vector and a pseudoscalar meson. In absence of gluonium, the value of the mixing angle in the quark-flavour basis is found to be φP=(40.5±2.4) deg. In presence of gluonium, the values for the mixing angle and the gluonic content of the η' wave function are φP=(44.5±4.3) deg. and Zη'2=0.28±0.21, respectively. Corrections due to non-ideal ω-φ mixing are shown to be negligible. The newly reported values of B(J/ψ→ρπ) by the BABAR and BES Collaborations are crucial to get a consistent description of data

[en] Preliminary results for the Dalitz plot distribution of η'→ηππ decays in the frameworks of Large-N_c Chiral Perturbation Theory and Resonance Chiral Theory are given. We hope our results to be of some relevance for the present and forthcoming analysis of these decays at GAMS, CLEO, VES, KLOE-2, Crystal Ball, Crystal Barrel, WASA, and BES-III.

[en] We present a model for the decay D⁺→K^-π⁺π⁺. The weak interaction part of this reaction is described using the effective weak Hamiltonian in the factorization approach. Hadronic final state interactions are taken into account through the Kπ scalar and vector form factors fulfilling analyticity, unitarity, and chiral symmetry constraints. The model has only two free parameters that are fixed from experimental branching ratios. We show that the modulus and phase of the S wave thus obtained agree nicely with experiments up to 1.55 GeV. We perform Monte Carlo simulations to compare the predicted Dalitz plot with experimental analyses. Allowing for a global phase difference between the S and P waves of -65 deg., the Dalitz plot of the D⁺→K^-π⁺π⁺ decay, the Kπ invariant mass spectra and the total branching ratio due to S-wave interactions are well reproduced.