PROSPECTS FOR MEASURING THE B(S)(0)-(B)OVER-BAR(S)(0) MIXING RATIO-X(S)

We review and update results bearing on the phenomenon of particle-antiparticle mixing in the neutral beauty meson sector. Our main focus is on the mixing ratio x(s), defined as x(s) = (DELTAM)/GAMMA, relevant for B(s)0-B(s)0BAR mixing. We present theoretical estimates of this quantity in the standard model (SM) and find that x(s) = O(10), which makes time-dependent oscillation measurements mandatory. We also discuss estimates of x(s) in a number of extensions of the sm, some of which admit smaller values of x(s). Present and future experimental facilities where such measurements can be undertaken are reviewed on a case-to-case basis. These include the high luminosity LEP option, asymmetric threshold B-factories, the ep collider HERA, and hadron colliders, such as the Fermilab Tevatron, LHC and SSC.