We show that the quark mixing matrix can be parametrized in exactly unitary forms with the imaginary parts present only at the order of ${10}^{-3\mathrm{}}$. With $s_x=s_1$ and $s_y$ well determined, measurements of ${\epsilon }^{\prime }$ or other $\mathrm{CP}$-nonconservation effects can determine $s_z{s}_{\phi }$. Then after $\left|V_{\mathrm{ub}}\right|\simeq s_z$ is measured, $s_{\phi }$ is known. We also give a simple expression for the $\mathrm{CP}$ asymmetry in the $B^0-B^0$ mixing.

• Received 30 March 1984

DOI:https://doi.org/10.1103/PhysRevLett.53.1802