UC Irvine

We extend the range of predictions of the isosinglet (or vector) down quark model to the fully allowed physical ranges, and also update this with the effect of new physics constraints. We constrain the present allowed ranges of (Formula presented) and (Formula presented) γ, (Formula presented) and (Formula presented) In models allowing mixing to a new isosinglet down quark (as in (Formula presented) flavor changing neutral currents are induced that allow a (Formula presented) mediated contribution to (Formula presented) mixing and which bring in new phases. In (ρ,η), (Formula presented) and (Formula presented) plots for the extra isosinglet down quark model which are herein extended to the full physical range, we find new allowed regions that will require experiments on (Formula presented) and/or (Formula presented) to verify or to rule out an extra down quark contribution. © 1998 The American Physical Society.