An example of the Feynman diagrams contributing to this decay is shown in Fig. Lattice calculations are required to interpret most of the experimental results. This involves calculating quark propagators at five different masses, and then using these to extract hadron masses, decay constants, scattering amplitudes and various matrix elements. We are on target for completing this work, with about 80 lattices finished at present. In the following we present some highlights of our results for weak matrix elements.
All results are preliminary.
The idea is that mesons and baryons are extended objects, of typical size 0.5-1.0 fm, and so an operator which can efficiently create them should be of similar size. The new calculations are in large part a production run using the methods we had developed. The latter improvement is very important since it allows more reliable extrapolations to the physical up and down quark masses. In the quenched approximation the quark-antiquark component of this cloud is ignored. Properties of hadrons that are not particularly dependent on the quark-antiquark component, for example the masses, decay constants, and form factors, will not be changed substantially by quenching.