The $Z\to b\bar{b}$ Excess and Top Decay

Abstract

The apparent excess of $Z\to b\bar{b}$ events at LEP may be an indication of new physics beyond the standard model. However, in either the two-Higgs-doublet model or the minimal supersymmetric standard model, any explanation would lead to an important new decay mode of the top quark and suppresses the $t\to Wb$ branching fraction, which goes against what has been observed at the Tevatron. In the two-Higgs-doublet model, the branching fraction of $Z\to b\bar{b}$ + a light boson which decays predominantly into $b\bar{b}$ would be at least of order 10${}^{-4}$.

15 pages and 8 figures

References in corpus (5)

• Observation of Top Quark Production in Pbar-P Collisions
• Observation of the Top Quark
• A Global Fit of LEP/SLC Data with Light Superpartners
• $R_b$ in supersymmetric models
• Implications of the Recent Top Quark Discovery on Two Higgs Doublet Model

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• Effective lagrangian description of top production and decay
• SUSY Contributions to R_b and Top Quark Decay
• An Elusive Z' Coupled to Beauty
• Solutions to the R_b, R_c and alpha_s puzzles by Vector Fermions
• $R_b$ -- $R_c$ Crisis and New Physics
• Supersymmetry, Supergravity and R_b revisited in the light of LEP 2
• An R-Parity Breaking SUSY Solution to the R_b and ALEPH Anomalies
• Upper Bound on R_b in Two Higgs Doublet Model from Lepton Universality
• R_b in Supergravity Grand Unification with Non-universal Soft SUSY Breaking