  The separation of a heavy quark and antiquark pair leads to the formation of
a tube of flux, or "string", which should break in the presence of light
quark-antiquark pairs. This expected zero-temperature phenomenon has proven
elusive in simulations of lattice QCD. In an extension of work reported last
year we present clear evidence for string breaking in QCD with two flavors of
dynamical staggered sea quarks and apply our results to a simple three-state
mixing model for string breaking. We find that mixing is weak and falls to zero
at level crossing.
