The Chirality of $b$ Quark Couplings

This review addresses the question of the chirality of $b$ quark weak couplings from a theoretical and from a purely phenomenological point of view. Due to their small magnitude $b$ decay couplings are subject to possible large corrections from right-handed terms, on the one hand, and do not affect the weak interactions of the first two quark families in any observable manner, on the other hand. This motivated an $SU(2)_L\times SU(2)_R\times U(1)$ model with purely right-handed $b$-decay couplings. The model is consistent with experiments, including recent measurements of a lepton forward-backward asymmetry in $B\to D^*\ell\nu$ and of radiative $B$ decays. Parity violating asymmetries in semileptonic decays of polarized $\Lambda_b$ baryons produced in $Z^0$ decays provide a promising way of measuring the chirality of the $b$ to $c$ current.