Leptonic signals for nonstandard heavy quarks

Alternatives to the standard sequential six-quark and six-lepton model of weak and electromagnetic interactions include several in which heavy quarks decay only semileptonically. The rates of inclusive and several semi-inclusive lepton-production channels in e+e- annihilation are estimated for such models and a comparison is made with the standard-model expectations. Consideration is given to lepton spectra, and it is pointed out that a hard spectrum could be the signal of purely leptonic decay of heavy, spinless hadrons. The latter process is predicted to be prominent in several alternative schemes, one of which is outlined here. The leptonic spectrum appears to provide a realistic method of detecting unexpected hadronic physics. Even if the b quark turns out to be of standard sequential type, it is stressed that it is important to test for anomalies in leptonic production rate and spectrum shape at higher PEP and PETRA energies