Neutral kaon mixing from new physics: Matrix elements in Nf=2+1 lattice QCD

We present results for matrix elements of Delta S = 2 four-fermion operators arising generically in models of new physics. These are needed to constrain such models using the measured values of epsilon(K) and Delta M-K. We use lattice QCD with 2 + 1 flavors of improved staggered fermions on lattices generated by the MILC Collaboration. We extrapolate to the continuum from three lattice spacings ranging down to a approximate to 0.045 fm. Total errors are similar to 5%-6%, arising primarily from our use of one-loop matching between lattice and continuum operators. For two of the matrix elements, our results disagree significantly from those obtained using different fermion discretizations.