Remarks on the mass scales, mixing angles, and signatures of the fourth-generation quarks

Assuming that the fourth family makes an appreciable contribution to /ital B/ mixing, assuming some mild properties of the (4/times/4) Cabibbo-Kobayashi-Maskawa matrix, and taking the lattice determination of the pseudoscalar decay constant for /ital B/ seriously, we arrive at a lower bound on /ital m//sub /ital t//, i.e., /ital m//sub /ital t//prime///approx gt/500 GeV. If perturbative unitarity is to be preserved, i.e., /ital m//sub /ital t//prime///similar to/500 GeV, then our analysis also implies that the top quark is unlikely to be lighter than /approx/80 Gev. Experimental consequences for rare /ital B/ decays, and /ital CP/ violation in /ital B/ decays are also discussed.