Implications of LEP/SLD Data for New Physics in Zbb_bar Couplings

摘要

The combined LEP/SLD data on the bar b forward-backward asymmetry from theZ-pole measurements may imply the presence of new physics in the $Zbar b$couplings. In general, the effect of new physics can be parameterized by$SU_C(3)imes SU_L(2)imes U_Y(1)$ invariant higher dimensional operators. Byfitting the recently announced LEP/SLD data on A_b and R_b, the size of thecoupling strengths of these operators can be determined. We also found that thenew physics operators can be divided into two types, depending on their Higgsfield content. The ones involving the Higgs have very mild effects at higherenergy colliders, while the other type which do not contain the Higgs field canshow significantly large effects on $bar b$ production at LEP II, $tar t$production at the NLC and single top production at the Tevatron. Thepreliminary data from the LEP II measurements disfavors the second type ofoperators.