Sigma meson in QCD sum rules using a two-quark current with derivatives

We study the σ meson in QCD sum rules using a two-quark interpolating field with derivatives. In the constituent quark model, the σ meson is composed of a quark and an antiquark in the relative p-wave state and is thus expected to have a larger overlap with an interpolating field that measures the derivative of the relative quark wave function. While the sum rule with a current without derivative gives a pole mass of around 1 GeV, the present sum rule with derivative current gives a mass of around 550 MeV and a width of 400 MeV, that could be identified with the σ meson.