By use of unitarity of the Kobayashi-Maskawa matrix, the rephasing-invariant measure ${\delta }_{\mathrm{KM}}$ of $\mathrm{CP}$ nonconservation is evaluated in terms of the moduli squared of four matrix elements, which are taken as the four independent parameters. The striking feature of such a formulation is that the positivity of ${\delta }_{\mathrm{KM}}^2$ gives both upper and lower bounds on the matrix elements $\left|V_{\mathrm{cd}}\right|$, $\left|V_{\mathrm{cs}}\right|$, $\left|V_{\mathrm{td}}\right|$, and $\left|V_{\mathrm{ts}}\right|$.

• Received 25 November 1987

DOI:https://doi.org/10.1103/PhysRevLett.61.35