Analysis the $f_0(980)$ and $a_0(980)$ mesons as four-quark states with the QCD sum rules

In this article, we take the point of view that the scalar mesons $ f_0(980)$ and $a_0(980)$ are diquark-antidiquark states, and derive the QCD sum rules for the interpolating currents composed of scalar-scalar type and pseudoscalar-pseudoscalar type diquark pairs respectively. The numerical results indicate that the scalar mesons $ f_0(980)$ and $a_0(980)$ may have two possible diquark substructures