Diquark correlations play an important role in hadron physics. The properties
of diquarks can be obtained from the corresponding bound state equation. Using
a model for the effective quark-quark interaction that has proved successful in
the light meson sector, we solve the scalar diquark Bethe-Salpeter equations
and use the obtained Bethe-Salpeter amplitudes to compute the diquarks'
electromagnetic form factors. The scalar ud diquark charge radius is about 8%
larger than the pion charge radius, indicating that these diquarks are somewhat
larger in size than the corresponding mesons. We also provide analytic fits for
the form factor over a moderate range in Q^2, which may be useful, for example,
in building quark-diquark models of nucleons.Comment: 11 pages, 3 .eps figures, minor corrections in table and figure, no
change in conclusion