Kl3 semileptonic form factor from 2 + 1 flavor lattice QCD

We present the first results for the Kl3 form factor from simulations with 2+1 flavors of dynamical domain wall quarks. Combining our result, namely, f+(0)=0.964(5) with the latest experimental results for Kl3 decays leads to |Vus|=0.2249(14), reducing the uncertaintity in this important parameter. For the O(p6) term in the chiral expansion we obtain f=-0.013(5).