Constraints on the mixing of a fourth family of quarks

This paper studies the constraints on the mixing of a possible fourth family of quarks. A mixing angle convention is introduced in which sij - sin 8ij represents to a good approximation the ij element of the quark mixing matrix (; < j). A range of parameters is found, ~14 < 0.06, ~24 < 0.1; s14s24 - O(10V4 - 10A3) and/or ~14~34 2 O(10m2), f or which the contribution of the fourth family to the KL - KS mass difference is negligible yet may lead to dominant effects in the K" - K' CP impurity parameter 6. This may be realized in a scheme in which the four quark generations are mixed mostly in pairs. A possible signature of such a scheme may be an abundant rate of same-sign dileptons at Y(4S) if the fourth up-type quark is sufficiently heavy.