Gregory Kilcup and Dmitry Pekurovsky, The Ohio State University

Research Objectives

Our objectives are computation of non-perturbative renormalization for staggered weak operators; computation of matrix elements for parameters B7 and B8; comparison of quenched and dynamical matrix element and quark mass results using QCDSP (Quantum Chromodynamics on Digital Signal Processors) configurations; and providing an archive of valuable gauge configuration data which can be used by the lattice community at large.

Computational Approach

We use Monte Carlo methods, fast Fourier transforms, and standard linear solvers including conjugate gradients and minimal residual.

Accomplishments

Using Grand Challenge resources at NERSC, we have computed the weak matrix elements which are responsible for the I = 1/2 rule. This is a longstanding puzzle of weak kaon decays, in which two seemingly similar decay processes (I = 0 and I =2) proceed at very different rates. For the I = 2 amplitudes, we were able to run on a whole ensemble of quenched gauge configurations and extrapolate to the continuum limit. For the more difficult I = 0 amplitudes, we ran at two quenched lattice spacings and on one small dynamical ensemble. To compute the matrix elements for , we find we also need to do a nonperturbative renormalization. As a first step in this direction, we have computed the light quark mass renormalization.

As a service to the whole lattice QCD community, we have also gauge-fixed all the configurations used and archived them in the qcd.nersc.gov archive.

Significance

	Visualization of typical fluctuations in the quark field. The underlying data are four-dimensional, and we show all four possible projections (x, y, z, t) down to 3D arranged as a tesseract.

As a field, lattice QCD provides theoretical calculations of quantities which can be measured experimentally. This provides both cross-checks of the Standard Model of particle physics, and a determination of several of its fundamental parameters. This work in particular is aimed at quark masses and certain weak interaction matrix elements using staggered fermions. In conjunction with results from other groups using different fermion formulations (e.g., Wilson, improved, domain wall), this research will help refine the theoretical calculation of the recently measured quantity .

Publications

D. Pekurovsky and G. Kilcup, "Lattice calculation of matrix elements relevant for I = 1/2 rule and ," e-print hep-lat/9903025 (1999).

D. Pekurovsky and G. Kilcup, "Matrix elements relevant for I = 1/2 rule and from lattice QCD with staggered fermions," e-print hep-lat/9812019 (1998).

D. Chen, G. Kilcup et al., "QCDP: A status report," Nucl. Phys. Proc. Suppl. 63, 997 (1998).

http://www.physics.ohio-state.edu/~kilcup/Lattice_QCD/
http://qcd.nersc.gov/