Lecture on a Z' Coupled to Beauty and Truth

Abstract

By extending the standard gauge group to $SU(3{)}_c\times SU(2{)}_L\times U(1{)}_Y\times U(1{)}_X$ with $X$ charges carried only by the third family we accommodate the LEP measurement of $R_b$ and predict a potentially measurable discrepancy in $A_{FB}^b$ in $e^{+}{e}^{-}$ scattering and that $D^0{\bar{D}}^0$ mixing may be near its experimental limit. The uniqueness of our model is that the Z' couplings are generation-dependent and hence explicitly violate the GIM mechanism, but can nevertheless be naturally consistent with FCNC constraints. Direct detection of this Z' is possible but challenging.

arXiv comment12 pages, latex including 3 Figures. Lecture at Ettore Majorana International School of Subnuclear Physics, Erice, Sicily, July 1996. This lecture is an updated version of hep-ph/9604260 by P.H.Frampton, M.B. Wise and B.D. Wright. Sections in italics, and the Figures, explain how this same model-building strategy (with different details) can accommodate different data on $R_b$ and $A^b$