Production and decay properties of ultra-heavy quarks☆

Abstract The widths of ultra-heavy quarks that can be decay into W, Z or Higgs bosons are discussed. If the lifetimes become much shorter than the typical strong interaction time scale Λ −1 QCD ∼ 10 −23 s, then open-flavor hadrons and quarkonium bound states cannot be formed any more. Consequences for the jet evolution are investigated. On the other hand, if such quarks can decay only through tiny mixing angles - as it could happen for sequential down-type quarks and for SU(2) singlet quarks in E 6 models - then these bound states do form. Production rates for quarkonia in e + e - annihilation and in hadronic collisions are estimated and their decay signatures are discussed.