Implications of high precision experiments and the CDF top quark candidates

We discuss the consequences of recent experimental results from CDF, SLC, CERN LEP, and elsewhere for the standard model and for new physics, A global fit to all indirect precision data yields ${\mathit{m}}_{\mathit{t}}$=175±${11}_{\mathrm{-}19}^{+17\mathrm{}}$ GeV, ${\sin }^2$θ${\mathrm{^}}_{\mathrm{MS}}$¯=0.2317(3)(2), and ${\mathrm{\alpha }}_{\mathit{s}}$=0.127(5)(2), where the central values are for ${\mathit{M}}_{\mathit{H}}$=300 GeV and the second uncertainties are for ${\mathit{M}}_{\mathit{H}}$→1000 GeV (+) and 60 GeV (-). The ${\mathit{m}}_{\mathit{t}}$ value is in remarkable agreement with the value ${\mathit{m}}_{\mathit{t}}$ value is in remarkable agreement with the value ${\mathit{m}}_{\mathit{t}}$=174±16 GeV suggested by the CDF candidate events. There is a slight preference for a light Higgs boson with ${\mathit{M}}_{\mathit{H}}$${\mathit{m}}_{\mathit{t}}$ value is (not) included. The sensitivity is, however, due almost entirely to the anomalously large observed values for the Z→bb¯ width and left-right asymmetry. The value of ${\mathrm{\alpha }}_{\mathit{s}}$ (from the line shape) is clean theoretically assuming the standard model, but is sensitive to the presence of new physics contributions to the Z→bb¯ vertex. Allowing a vertex correction ${\mathrm{\delta }}_{\mathit{b}\mathit{b}}^{\mathrm{new}}$ one obtains the significantly lower value ${\mathrm{\alpha }}_{\mathit{s}}$=0.111±0.009, in better agreement with low energy determinations, and ${\mathrm{\delta }}_{\mathit{b}\mathit{b}}^{\mathrm{new}}$=0.023±0.011.