Measuring gamma cleanly with CP-tagged Bs and Bd decays

We propose a new method for measuring the CKM phase gamma using the partial rates for CP-tagged Bs decays. Such an experiment could be performed at a very high luminosity symmetric e+e- collider operating at the Upsilon(5S) resonance, where the Bs-Bsbar state is produced in a state of definite CP. We also discuss CP-tagging in the Bd system at the Upsilon(4S), where a time-dependent analysis is required to compensate for the anticipated large CP violation in Bd-Bdbar mixing.