ar X iv : h ep - p h / 98 03 24 9 v 1 5 M ar 1 99 8 KAIST – TH – 98 / 04 New Electroweak Tests for the Topflavour Model
نویسندگان
چکیده
In this work we consider the model with additional SU(2) acting only on the third generation, which has been suggested by several authors 1,2 as a possible solution of the Rb problem. The third generation undergoes different flavour dynamics from the first and second generations and we expect that this type of model would help us to explain the discrepancy of Rb of which measurement is about 1.8 (LEP) and 1.5 (LEP+SLC) standard deviations higher than the SM prediction. As an analogy to the topcolor model , this model is called topflavour model . In order to parametrize new physics effects on the observables from the LEP experiments, we calculate the precision variables ǫi’s introduced by Altarelli et al. 4,5 with the new LEP data reported by the LEP Electroweak Working Group 6 in the framework of the topflavour model. Because there is no direct evidence for new physics beyond the Standard Model (SM) at LEP until now, the new physics contribution, if it exists, are thought to be comparable with the radiative correction effects of the SM at most. Hence it will be interesting to study the new physics effects in terms of the precision variables. Among four epsilon variables, ǫb has been of particular interest because it encodes the corrections to the Z → bb̄ vertex and we focus on ǫb.
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