Heavy-quark symmetries in form factors at large recoil.

Abstract

It has recently been shown that hadrons containing a single heavy quark exhibit a new flavor-spin symmetry of QCD, and that this symmetry leads to relations between operator matrix elements involving such hadrons. On examining mechanisms that might break the symmetry at large recoil, I conclude that these relations are probably valid over the full kinematic ranges available in transitions involving $b\ensuremath{\rightarrow}c$, $b\ensuremath{\rightarrow}s$, $b\ensuremath{\rightarrow}u$, $c\ensuremath{\rightarrow}s$, and $c\ensuremath{\rightarrow}d$ currents.