The success of the Fritzsch mass-matrix Ansatz in reproducing the observed pattern of the Kobayashi-Maskawa mixings can be explained by having the mass matrices of the charge $\frac{2}{3}$ and $-\frac{1}{3}$ quarks closely proportional to each other. Thus except for light quarks, the ratio of these two masses in each generation should be the same. Extending this to the fourth generation and using the electroweak $\rho$-parameter constraint we expect that the fourth charged lepton and the seventh (down type) and the eighth (up type) quarks, if they exist, are likely to have masses around 25, 60, and 450 GeV, respectively.

• Received 10 September 1985

DOI:https://doi.org/10.1103/PhysRevLett.55.2249