Abstract
In models with more than one Higgs doublet, the Yukawa couplings of the d-type (u-type) quarks are changed by a factor (), which is often a ratio of vacuum expectation values. Abbott, Sikivie, and Wise showed that the - mass difference places stringent constraints on (≲10 for a charged-Higgs-boson mass of ); however, this bound is very sensitive to the charged-Higgs-boson mass and to small Kobayashi-Maskawa mixing angles. We note that if the enhancement is greater than 4–5, then the top quark’s Yukawa coupling will exceed its strong coupling, even if ∼35 GeV. The effects of this enhancement on the cross section, on energy levels, leptonic widths, and decay rate of t-quarkonium, and on top-quark decays are discussed; the former two effects are sensitive to neutral-scalar masses only, the latter to the charged-Higgs-boson mass; all of the effects are insensitive to small mixing angles. We also note that the best limit on comes from recent data on the semileptonic branching ratio of b quarks.
- Received 16 July 1984
DOI:https://doi.org/10.1103/PhysRevD.31.95
©1985 American Physical Society