Qualitative Signals of New Physics in B-Bbar Mixing

It is expected that, within the next three years, the determination of the CKM matrix elements with the least theoretical uncertainty will arise from the measurements of CP violation in B_d --> J/\psi K_S decays and from Bs-Bsbar mixing. If there is significant new physics in Bs-Bsbar mixing, then those experiments will not yield the correct values for the CKM matrix elements. As a result, a qualitative signal of new physics may appear in the CP violation of decays like B_d --> pi+ pi-.