Study ofbcouplings in the standard weak doublet model and in models without atquark

In the context of five-quark models without a $t$ quark, both left-handed $b$-singlet and right-handed $b$-doublet options are of interest. We explore the implications of these models, contrasting their predictions with those of the standard six-quark model. In $B$-meson decays, the singlet model predicts neutral-current modes at a significant level, whereas the ${\mathrm{}(c,b)\mathrm{}}_R$ model more closely resembles the standard model. The soft and hard components of the single-lepton energy spectrum can both be used to discriminate between the three classes of models. In neutrino interactions the most promising mechanism is $b$ production from $c$ quarks, which we study in the gluon-fusion and intrinsic-charm models. The $b$ cross section is much larger for the ${\mathrm{}(c,b)\mathrm{}}_R$ model. Rates for multilepton final states that might be realized from decays of $b$ and its associated charm spectator are discussed.