Jeonghwan Pak

Improved determination of B-K with staggered quarks

obtained using improved staggered fermionson a much enlarged set of MILC asqtad lattices. Compared to our previous publication, which wasbased largely on a single ensemble at each of the three lattice spacings aˇ0:09 fm, 0:06 fm and0:045 fm, we have added seven new ne and four new super ne ensembles, with a range of valuesof the light and strange sea-quark masses. We have also increased the number of measurementson one of the original ensembles. This allows us to do controlled extrapolations in the light andstrange sea-quark masses, which we do simultaneously with the continuum extrapolation. Thisreduces the extrapolation error and improves the reliability of our error estimates. Our nal resultis B^

Improved determination of BK with staggered quarks

obtained using improved staggered fermionson a much enlarged set of MILC asqtad lattices. Compared to our previous publication, which wasbased largely on a single ensemble at each of the three lattice spacings aˇ0:09 fm, 0:06 fm and0:045 fm, we have added seven new ne and four new super ne ensembles, with a range of valuesof the light and strange sea-quark masses. We have also increased the number of measurementson one of the original ensembles. This allows us to do controlled extrapolations in the light andstrange sea-quark masses, which we do simultaneously with the continuum extrapolation. Thisreduces the extrapolation error and improves the reliability of our error estimates. Our nal resultis B^

Non-perturbative Renormalization of Bilinear Operators on Fine Lattice

We present results of the wave function renormalization factor Zq and mass renormalization factor Zm obtained using non-perturbative renormalization (NPR) method in the RI-MOM scheme with HYP improved staggered quarks. We use fine ensembles of MILC asqtad lattices (N f = 2+ 1) with 283×96 geometry, a≈ 0.09 fm, and am`/ams = 0.0062/0.031. We also study on scalability of Zq and Zm by comparing the results on the coarse and fine ensembles.

Performance of GTX Titan X GPUs and Code Optimization

Recently Nvidia has released a new GPU model: GTX Titan X (TX) in a linage of the Maxwell architecture. We use our conjugate gradient code and non-perturbative renormalization code to measure the performance of TX. The results are compared with those of GTX Titan Black (TB) in a lineage of the Kepler architecture. We observe a significant gain in the single and double precision calculations much greater than the theoretical expectation.

Nonperturbative Renormalization in the RI-SMOM Scheme and Gribov Uncertainty in the RI-MOM Scheme for Staggered Bilinears

We present results of renormalization factors for bilinear operators obtained using the nonperturbative renormalization method (NPR) in the RI-SMOM schemes. The operators are constructed using HYP staggered quarks on the MILC asqtad lattice (N f = 2+1). We compare results in the RI-SMOM schemes with those in the RI-MOM scheme for the V ⊗S and S⊗S operators. Since we use Landau gauge fixing, we study the effect of Gribov ambiguity on the wave function renormalization Zq in the RI-MOM scheme. We find that the Gribov uncertainty is negligibly small for Zq in the RI-MOM scheme.

Non-perturbative Renormalization of Four-fermion Operators Relevant to B_K with Staggered Quarks.

We present preliminary results of matching factors of the four-fermion operators relevant to

Recent update on

B_K

B_K

, which are obtained using the non-perturbative renormalization (NPR) method in the RI-MOM scheme with HYP-smeared improved staggered fermions. We use the MILC asqtad coarse (

and

a \cong 0.12\,

\varepsilon_K

fm) ensembles with