  The hypervelocity stars recently found in the Galactic halo are expelled from
the Galactic center through interactions between binary stars and the central
massive black hole or between single stars and a hypothetical massive binary
black hole. In this paper, we demonstrate that binary stars can be ejected out
of the Galactic center with velocities up to 10^3 km/s, while preserving their
integrity, through interactions with a massive binary black hole. Binary stars
are unlikely to attain such high velocities via scattering by a single massive
black hole or through any other mechanisms. Based on the above theoretical
prediction, we propose a search for binary systems among the hypervelocity
stars. Discovery of hypervelocity binary stars, even one, is a definitive
evidence of the existence of a massive binary black hole in the Galactic
center.
