BK from quenched QCD with exact chiral symmetry

We present a calculation of the standard model DeltaS=2 matrix element relevant to indirect CP violation in K-->pipi decays which uses Neuberger's chiral formulation of lattice fermions. The computation is performed in the quenched approximation on a 16(3) x 32 lattice that has a lattice spacing a approximately 0.1 fm. The resulting bare matrix element is renormalized nonperturbatively. Our main result is B(RGI)(K)=0.87(8)+2+14-1-14, where the first error is statistical, the second is systematic, and the third is Sharpe's estimate of quenching and flavor-SU(3) breaking uncertainties.