In view of the experimental indications that the top-quark mass may exceed the upper bound predicted by the Fritzsch ansatz for the quark mass matrices, we follow a phenomenological approach to find a modified form of the mass matrices to deal with quark mixing and $\mathrm{CP}$ violation in electroweak interactions. The essential feature of our mass matrices is that the diagonal elements corresponding to the light quarks $u$, $d$, and $s$ are vanishingly small, while those corresponding to the heavy quarks $c$, $b$, and $t$ are approximately equal to the observed values of their masses. By comparing our theoretical results for the Kobayashi-Maskawa mixing matrix elements with the experimental data, we obtain for the top-quark mass and the $\mathrm{CP}$-violating phase the values $m_t^{\mathrm{phys}}\le 170$ GeV and $91°\le \delta \le 105°$.

• Received 25 March 1991

DOI:https://doi.org/10.1103/PhysRevD.44.2110