The charmed-strange meson spectrum is calculated with the overlap valence fermions on 2+1 flavor domain wall dynamical configurations for $32^3times 64$ lattices with a spatial size of 2.7 fm. Both charm and strange quark propagators are calculated w
ith the overlap fermion action. The calculated scalar meson at 2304(22) MeV and axial-vector meson at 2546(27) MeV are in good agreement with the experimental masses of $D{s0}^*$(2317) and $D_{s1}$(2536).
The charmed-strange meson masses are calculated on a quenched lattice QCD. The charm and strange quark propagators are calculated on the same lattice with the overlap fermion. $16^3times 72$ lattice with Wilson gauge action at $beta=0.6345$ are used.
The charm and strange quark masses are determined by fitting the $J/psi$ and $phi$ masses respectively. The charmed strange meson spectrum for the scalar, axial, pseudoscalar and vector channels are calculated. They agree with experiments. In particular, we find the scalar meson mass to be 2248(78)MeV which is in agreement with that of D_{s0}^*(2317).
In this talk, we shall assess the finite ma errors from the overlap fermion. We shall present results on the speed of light from the dispersion relation and hyperfine splitting between the vector and pseudoscalar mesons as a function to ma to reveal
the mLambda_{QCD}a^2 and m^2a^2 errors. We conclude from this study that one should be limited to using ma less than 0.5 in order to keep the systematic ma errors below a few percent level.
