One-loop matching of improved four-fermion staggered operators with an   improved gluon action
  We present results for one-loop matching factors of four-fermion operators composed of HYP-smeared staggered fermions. We generalize previous calculations by using the tree-level improved Symanzik gauge action. These results are needed for our companion numerical calculation of $B_K$ and related matrix elements. We find that the impact on one-loop matching factors of using the improved gluon action is much smaller than that from the use of either HYP smearing or mean-field improvement. The one-loop coefficients for mean-field improved, HYP-smeared operators with the Symanzik gauge action have a maximum magnitude of $O(1)\times \alpha_s$, indicating that perturbation theory is reasonably convergent. 
Jongjeong Kim, Weonjong Lee, and Stephen R. Sharpe
hep-lat hep-ph