title: Direct mass limits for chiral fourth-generation quarks in all mixing scenarios.
abstract: Present limits on chiral fourth-generation quark masses mb' and mt' are broadly generalized and strengthened by combining both t' and b' decays and considering a full range of t' and b' flavor-mixing scenarios with the lighter generations (to 1-‖V44‖2≈10(-13)). Various characteristic mass-splitting choices are considered. With mt'>mb' we find that CDF Collaboration limits on the b' mass vary by no more than 10%-20% with any choice of flavor mixing, while for the t' mass, we typically find stronger bounds, in some cases up to mt'>430  GeV. For mb'>mt', we find mb'>380-430  GeV, depending on the flavor mixing and the size of the mt'-mb' mass splitting.
authors.affiliation: Department of Physics and Astronomy, University of California, Irvine, California 92697, USA. cflacco@mac.com
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Flacco
authors.forename: Daniel
authors.initials: D
authors.lastname: Whiteson
authors.forename: Tim M P
authors.initials: TM
authors.lastname: Tait
authors.forename: Shaouly
authors.initials: S
authors.lastname: Bar-Shalom