The φ(1020)→π0π0γ decay

Radiative ϕ decays with derivative interactions

“…Being the coupling to kaons of particular theoretical interest we perform the fit for different values of c f0KK . We start setting c f0KK = 0 ; the fit is done to the experimental data of SND and KLOE collaborations [20,21] corresponding to the black and grey dots in Fig. 3 retaining the data points above 0.6 GeV.…”

“…We thus not intend to state that c f0KK is small (what would be in conflict with data from ππ scattering) but only that its determination from the line shape is problematic when mechanism a.1 (whose amplitude is proportional to c f0ππ ) is regarded as dominant. We consider data sets from the SND and KLOE collaborations [20,21] corresponding respectively to the black and grey (green online) dots. The continuous line is the result of the fit by setting c f 0 KK = 0, the dashed line corresponds to the case c f 0 KK = 12 GeV −1 .…”

Scalar meson exchange in θ → P0P0γ decays

“…For the branching ratio they obtain B(φ → π 0 π 0 γ) = (1.221 ± 0.098 ± 0.061) × 10 −4 [1] and (1.08 ± 0.17 ± 0.09) × 10 −4 [2]. More recently, the KLOE Collaboration has measured B(φ → π 0 π 0 γ) = (1.09 ± 0.03 ± 0.05) × 10 −4 [3].…”

“…A first model including the scalar resonances explicitly is the no structure model, where the V → P 0 P 0 γ decays proceed through the decay chain V → Sγ → P 0 P 0 γ and the coupling V Sγ is considered as pointlike. This model is ruled out by experimental data on φ → π 0 π 0 γ decays [1]. A second model is the kaon loop model [8], where the initial vector decays into a pair of charged kaons that, after the emission of a photon, rescatter into a pair of neutral pseudoscalars through the exchange of scalar resonances.…”

Radiative decays with scalar mesons and in Resonance Chiral Theory

“…The e + e − experiments in Novosibirsk [1,2] and Frascati [3,4] allow one to study the φ(1020) → ππγ (and πηγ) radiative decays. The invariant mass distributions of the pseudoscalar (P ) pairs in these decays are of considerable interest.…”