$Z \to b {\bar b}$ in a composite model of fermions

Abstract

A composite model of fermions is proposed to explain the "anomaly" in $Z \rightarrow b {\bar b}$ and, to a lesser extent, in $Z \rightarrow c {\bar c}$. It contains a {\em nonsequential} fourth family whose mass of one member (the charge -1/3 quark) is constrained to be between 47 GeV and 49 GeV. The charge +2/3 quark is constrained to lie between 67 GeV and 107 GeV. This opens up the exciting prospect for near-future discoveries at LEP2 and possibly at the Tevatron.