  We calculate diquark correlation functions in the Landau gauge on the lattice
using overlap valence quarks and 2+1-flavor domain wall fermion configurations.
Quark masses are extracted from the scalar part of quark propagators in the
Landau gauge. Scalar diquark quark mass difference and axial vector scalar
diquark mass difference are obtained for diquarks composed of two light quarks
and of a strange and a light quark. Light sea quark mass dependence of the
results is examined. Two lattice spacings are used to check the discretization
effects. The coarse and fine lattices are of sizes $24^3\times64$ and
$32^3\times64$ with inverse spacings $1/a=1.75(4) {\rm~GeV}$ and $2.33(5)
{\rm~GeV}$, respectively.
