Form factors and wave functions in Coulomb gauge

In the static approximation, the charge density distribution of the light quark in a heavy-light system is a physical observable. This form factor ( left angle Bvertical stroke j0q( vector x)vertical stroke B right angle ) may be extracted from the lattice by putting the current at the light propagator source point and tying it to the static line a distance vector x away at some positive and negative time slice. When the heavy line connection is smeared at both ends using a source function derived from the Coulomb-gauge wave function, the result is a stable extraction of the charge density. (orig.)