The RBC and UKQCD collaborations have been producing domain wall fermion (DWF) lattices with 2+1 flavors of quarks for a few years. With our 2007-2008 USQCD allocation for kaon physics, we will be making light quark propagators for the evaluation of the kaon bag parameter, BK, which is needed to relate indirect CP violation experimental results to the standard model.

The RBC and UKQCD collaborations have recently published a Physical Review Letter about BK, based on our results from 2+1 flavor DWF QCD. This work was done on lattices with spatial extent of 2.74 fm and a lattice spacing of 0.11 fm. We determined BK to be 0.524(10)(28) in the MS-bar renormalization scheme at a renormalization scale of 2 GeV. The paper, Physical Review Letters 100, 032001 (2008), can be found on arXiv here .

With the 2007-2008 USQCD allocation, we will repeat our BK calculation on lattices of similar physical volume, but with a lattice spacing of about 0.08 fm. In particular, we will be measuring quark propagators for BK on the 32^3 x 64 x 16 lattices listed here. These lattices are being generated with the UKQCD QCDOC and with the USQCD QCDOC, as part of another USQCD allocation. We will be solving the five -dimensional Dirac equation for domain wall fermions, using a four-dimensional Coulomb gauge fixed wall source. The resulting quark propagators will be projected back to four-dimensional propagators, and stored to disk for use by others. Propagators will be found for both periodic and anti-periodic boundary conditions in time and both cases will be stored to disk. We expect to use around 5 valence masses in these calculations.

These calculations should begin in February, 2008, since the needed configurations will have been generated by then.