Probing the structure of $f_0(980)$ through radiative $ϕ$ decays

Abstract

We consider the radiative transition $ϕ\to f_0 γ$, which is a sensitive probe of the nature of the $f_0(980)$ particle. Using the QCD sum-rule technique, we estimate the branching ratio of such decay mode to be: ${\cal B}(ϕ\to f_0 γ)=(2.7 \pm 1.1) ~ 10^{-4}$, in fair agreement with present experimental data. As for the structure of the $f_0$, the result suggests a sizeable $s {\bar s}$ component; however, this result does not exclude the possibility of further components and allows a more complex structure than indicated by the naive quark model.