  The di-electron width of an Upsilon meson is the decay rate of the Upsilon
into an electron-positron pair, expressed in units of energy. We measure the
di-electron width of the Upsilon(1S) meson to be 1.354 +- 0.004 +- 0.020 keV
(the first uncertainty is statistical and the second is systematic), the
di-electron width of the Upsilon(2S) to be 0.619 +- 0.004 +- 0.010 keV and that
of the Upsilon(3S) to be 0.446 +- 0.004 +- 0.007 keV. We determine these values
with better than 2% precision by integrating the Upsilon production
cross-section from electron-positron collisions over their collision energy.
Our incident electrons and positrons were accelerated and collided in the
Cornell Electron Storage Ring, and the Upsilon decay products were observed by
the CLEO-III detector. The di-electron widths probe the wavefunctions of the
Strongly-interacting bottom quarks that constitute the three Upsilon mesons,
information which is especially interesting to check high-precision Lattice QCD
calculations of the nuclear Strong force.
