GW Meson Scattering on a Staggered Sea

We discuss the structure of the NLO corrections to the chiral formulae for mesonic scattering processes in mixed action simulations using Ginsparg-Wilson valence quarks and staggered sea quarks. In particular, we show that the analytic contribution of the NLO chiral Lagrangian is the same as in QCD. We also comment on how this result restricts the dependence of the amplitudes on the unknown parameter C_Mix appearing in the chiral theory appropriate for these systems. We conclude with some comments on the explicit scattering lengths.