Rb and new physics: A comprehensive analysis

We survey the implications for new physics of the discrepancy between the measurement of Rb at the CERN e+e- collider LEP and its standard model prediction. Two broad classes of models are considered: (i) those in which new Zb¯b couplings arise at the tree level, through Z or b-quark mixing with new particles, and (ii) those in which new scalars and fermions alter the Zb¯b vertex at one loop. We keep our analysis as general as possible in order …