Weak interactions of ultra heavy fermions (II)

Abstract

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The effects of the fourth generation on the double-lepton polarization in theB→Kℓ+ℓ−decay

“…However, the common mass of the fourth quark (m t ′ ) lies between 320 GeV and 730 GeV with respect to the experimental value of ρ = 1.0002 +0.0007 −0.0004 [11]. The last value is close to the upper limit on heavy quark masses, m q ≤ 700 GeV ≈ 4m t , which follows from partial-wave unitarity at high energies [12]. Flavor-changing neutral current (FCNC) b → s(d)ℓ + ℓ − decays provide important tests for the gauge structure of the standard model (SM) at oneloop level.…”

Fourth generation bound states

“…In addition, there is a "unitarity upper limit" on fourth generation quark mass of about 500 GeV [8,9]. This does not, however, necessarily forbid heavier quark masses.…”

t′ at the LHC: the physics of discovery

“…This range should be typical of a dynamically generated fermion mass if this is the mass of electroweak symmetry breaking, assuming no fine tuning in the underlying dynamics. Related to this is the old observation that 550 GeV is roughly the mass of a heavy quark above which its coupling to the Goldstone boson is strong [2]. For more discussion of the dynamics and structure of such a theory see [1].…”

“…In particular the mass splittings of the quark and lepton doublets and the relative sizes of the quark and lepton masses are constrained [1], and if such mass relations are observed then this would constitute good evidence. 2 The other is that our proposed signal involves the weak charged-current decay of new heavy fermions. In contrast new vector-like fermions may have dominant decay modes through gluon or Z emission.…”