Stech mass matrix with fourth-generation quarks.

Abstract

We study the Stech mass matrix with four generations using experimental values of the Kobayashi-Maskawa matrix elements. Masses of the fourth-generation quarks (a and v quarks) are allowed in the following region: 120\ensuremath{\lesssim}${m}_{a}$\ensuremath{\lesssim}370 GeV and 22\ensuremath{\lesssim}${m}_{v}$\ensuremath{\lesssim}60 GeV. The top-quark mass is constrained to be lower than 43 GeV. We also discuss the effect of the fourth-generation quark on CP violation in the ${K}^{0}$-K\ifmmode\bar\else\textasciimacron\fi{} $^{0}$ and ${B}^{0}$-B\ifmmode\bar\else\textasciimacron\fi{} $^{0}$ systems.