R. Kaiser, A. V. Manohar and T. Mehen, Isospin Violation in $e^+ e^- \rightarrow B \overline{B}$,
Phys. Rev. Lett. 90, 142001
(2003) [0208194] .
Abstract: The ratio of the B+ B- and B0 B0bar production rates in e+
e- annihilation is computed as a function of the B meson
velocity and BB* pi coupling constant, using a
non-relativistic effective field theory.