What can we learn from the $Z\to b\bar{b}$ vertex?

Abstract

I stress the fact that a complete study of possible New Physics effects in the $Z\to b\bar{b}$ vertex requires a combined analysis of the ratio $R_b=\Gamma (Z\to b\bar{b})/\Gamma (Z\to hadrons)$ and the longitudinally polarized forward backward asymmetry, $A_b$. This is illustrated with a number of models such as the two Higgs-doublet model, the MSSM, Technicolour and models with an extra $Z^{\prime }$. The use of effective lagrangean techniques is briefly discussed.

Comments: 4 pages,no figures, to appear in Proc. of XXXth Rencontres de Moriond Les Arcs France