The quark-gluon mixed condensate $g<\bar q \sigma_{ \mu\nu} F_{ \mu\nu} q>$ is calculated in the Gaussian approximation of the Field Correlator Method. In the large N_c limit and for zero mass quarks one obtains a simple result, $m^2_0 \equiv \frac{ g<\bar q \sigma_{ \mu\nu} F_{ \mu\nu} q>}{ <\bar q q>} = \frac{ 16\sigma}{ \pi}$, where $\sigma$ is the string tension. For a standard value $\sigma=0.18 GeV^2$ one obtains $m^2_0=1 GeV^2$ in good agreement with the QCD sum rules estimate $m^2_0 = (0.8\pm 0.2) GeV^2$ and the latest lattice result $m^2_0 \cong 1 GeV^2$.
Categories: hep-ph hep-lat