Test of Scalar Meson Structure in $ϕ$ Radiative Decays

Abstract

We show that $ϕ$ radiative decays into scalar mesons [$f_0$(975), $a_0$(980)$\equiv S$] can provide important clues on the internal structures of these mesons. Radiative decay widths vary widely: $B.R.=10^{-4}-10^{-6}$ depending on the substructures ($q\bar q$, $qq\bar q\bar q$, $K\bar K$, glueball). Hence, we could discriminate among various models by measuring these widths at future $ϕ$ factories. The understanding of these meson structures is valuable not only in hadron spectroscopy but also in nuclear physics in connection with the widely-used but little-understood $σ$ meson. We also find that the decay $ϕ\rightarrow Sγ\rightarrow K^0 \bar K^0γ$ is not strong enough to pose a significant background problem for studying CP violation via $ϕ\rightarrow K^0 \bar K^0$ at the $ϕ$ factories.