Research Objectives
To compute the theoretical rates for certain weak interaction decay modes of elementary particles, thereby helping constrain our knowledge of the Standard Model of particle physics.
Computational Approach
We use lattice gauge theory, a technique which discretizes space and time and models the quantum fluctuations in the vacuum by Monte Carlo. The propagation of quarks in random background fields is computed by solving discretized PDEs with conjugate gradients. These algorithms fit very naturally on parallel machines such as NERSC's T3E.
Accomplishments
Using several ensembles of lattices with varying lattice spacing, we were able to do a definitive continuum extrapolatation for one weak interaction quantity, BK, which gives the rate at which kaons turns themselves in to anti-kaons. In a similar vein we began the calculation of several quantities (prosaically known as B1 through B8), which enter in to the decay rate of kaons in to pions. Further calculations are required to determine their final values. Along the way we found the first evidence from a lattice calculation for the famous "delta I=1/2" rule in kaon decays, a longstanding and puzzling phenomenon in weak interactions.
Significance
Together with results from particle physics experiments currently underway at labs in the US and Europe, these calculations allow direct and detailed tests of the so-called Standard Model of particle physics. At a mininum they will help determine some of the fundamental constants of nature. Eventually such tests may find small gaps in our current understanding of particle interactions, thereby giving us clues as to the new physics which lies beyond.
Publications
G. Kilcup, R. Gupta and S. Sharpe. 1997. Staggered Fermion Matrix Elements Using Smeared Operators. E-print hep-lat/9707006, Physical Review D, in press.
D. Pekurovsky and G. Kilcup. 1997. Weak Matrix Elements: On the Way to the Delta I=1/2 Rule and Epsilon-Prime/Epsilon with Staggered Fermions. E-print hep-lat/9709146. Nuclear Physics B (Proc Supp), in press.
URL
http://www.physics.ohio-state.edu/~kilcup/Lattice_QCD
A visualization of the "quark propagator"
in one typical random background chromoelectric
field. A quark is created at the center of the image, and the color intensities show the
probability of finding it elsewhere. Red indicates a high probability; blue is the lowest. By
studying spatial and temporal correlations in the patterns of fluctuations, researchers can
discern properties of the strongly interacting particles.