An upper limit on CP violation in the $B_s^0-{\bar{B}}_s^0$ system

In a previous publication we noted that the time dependence of an incoherent $B^0-{\bar{B}}^0$ mixture undergoes a qualitative change when the magnitude of CP violation $\delta$ exceeds a critical value. Requiring, on physical grounds, that the system evolve from an initial incoherent state to a final pure state in a monotonic way, yields a new upper limit for $\delta$. The recent measurement of the wrong charge semileptonic asymmetry of $B_s^0$ mesons presented by the D0 collaboration is outside this bound by one standard deviation. If this result is confirmed it implies the existence of a new quantum mechanical oscillation phenomenon.