Lattice calculation of $\kappa$ meson

We study the $\kappa$ meson in 2+1 flavor QCD with sufficiently light $u/d$ quarks. Using numerical simulation we measure the point-to-point $\kappa$ correlators in the "Asqtad" improved staggered fermion formulation. We analyze those correlators using the rooted staggered chiral perturbation theory (rS$\chi$PT), particular attention is paid to the bubble contribution. After chiral extrapolation, we obtain the physical $\kappa$ mass with $828\pm97$ MeV, which is within the recent experimental value $800\sim900$MeV. These numerical simulations are carried out with MILC 2+1 flavor gauge configurations at lattice spacing $a \approx 0.12$ fm.