Analysis of the nature of the $ϕ\toγπη$ and $ϕ\toγπ^0π^0$ decays

Abstract

We study interference patterns in the $ϕ\to(γa_0+π^0ρ)\toγπη$ and $ϕ\to(γf_0+π^0ρ)\toγπ^0π^0$ reactions. Taking into account the interference, we fit the experimental data and show that the background reaction does not distort the $π^0η$ spectrum in the decay $ϕ\toγπη$ everywhere over the energy region and does not distort the $π^0π^0$ spectrum in the decay $ϕ\toγπ^0π^0$ in the wide region of the $π^0π^0$ system invariant mass, $m_{ππ}>670$ MeV, or when the photon energy is less than 300 MeV. We discuss the details of the scalar meson production in the radiative decays and note that there are reasonable arguments in favor of the one-loop mechanism $ϕ\to K^+K^-\toγa_0$ and $ϕ\to K^+K^-\toγf_0$. We discuss also distinctions between the four-quark, molecular, and two-quark models and argue that the Novosibirsk data give evidence in favor of the four-quark nature of the scalar $a_0(980)$ and $f_0(980)$ mesons.