Scalar f0(980) and sigma(500) meson exchange in phi decays into pi0pi0gamma

Abstract

The complementarity between Chiral Perturbation Theory and the Linear Sigma Model is exploited to study ${\pi }^0{\pi }^0$ production in $\varphi$ radiative decays, where the effects of the $f_0(980)$ scalar resonance, and those of its more controversial $\sigma (500)$ partner, should become manifest via the $\varphi \to K^{+}{K}^{-}(\gamma )\to {\pi }^0{\pi }^0\gamma$ decay chain. The recently reported data on $\varphi \to {\pi }^0{\pi }^0\gamma$ coming from the VEPP-2M $e^{+}{e}^{-}$ collider in Novosibirsk and the DA$\Phi$NE $\varphi$-factory in Frascati can be reasonably described in our approach, which we propose as a promising first step towards more detailed analyses. The $f_0(980)$ contribution, which appears as a moderately narrow peak at the high part of the dipion mass spectrum, can be interpreted as the isoscalar member of the scalar nonet with a large $f_{0}K\bar{K}$ coupling and an $f_0\pi \pi$ coupling suppressed by almost ideal $\sigma$-$f_0$ mixing. Indeed, the mixing angle in the flavour basis is found to be ${\varphi }_S\approx -6^{\circ }$, if the $f_0$-propagator is approximated by a simple Breit-Wigner, or ${\varphi }_S\approx -9^{\circ }$, if an improved two-channel analysis is performed. The $\sigma (500)$ resonance, which is then strongly coupled to pion pairs, yields a tiny contribution because, in our approach, its coupling to kaon pairs is proportional to $m_{\sigma }^2-m_K^2$ and thus quite small.

18 pages, 4 figures; new treatment of the f0 propagator added and Comments on previous work corrected

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Cited by in corpus (29)

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• The new analysis of the KLOE data on the phi->eta pi0 gamma decay
• The Mixing Angle of the Lightest Scalar Nonet
• Properties of the light scalar mesons face the experimental data on the $\varphi \to {\pi }^0{\pi }^0\gamma$ decay and the $\pi \pi$ scattering
• Unitary chiral dynamics in J/Psi to VPP decays and the role of scalar mesons
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• Mixing of Pentaquark and Molecular States
• Radiative phi decays
• Asymmetry observables in e+ e- --> pi+ pi- gamma in the phi region within a chiral unitary approach
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• Scalar meson exchange in phi->P0P0gamma decays
• Scalar meson exchange in V->P0P0gamma decays
• Chiral Dynamics of scalar mesons: radiative $\varphi$ decay and $\sigma$ in the medium through ${\pi }^0{\pi }^0$ nuclear photoproduction