Spin Symmetry Without Heavy Quarks: Hyperon Form Factors In The Large $N_c$ Limit

Abstract

In the large $N_c$ limit, all hyperon decays involving the same quark diagram $Q\to Q^{\prime }$ are described by a single weak form factor ${\eta }_{Q{Q}^{\prime }}(w)$. No assumption on the mass of $Q$ or $Q^{\prime }$ is necessary, making our results applicable to both $b\to c$ and $c\to s$ transitions. This same form factor describes both ${\Lambda }_Q\to {\Lambda }_{Q^{\prime }}$ and ${\Sigma }_Q^{(\ast )}\to {\Sigma }_{Q^{\prime }}^{(\ast )}$ transitions. The (non-)commutativity between the heavy quark and the large $N_c$ limits is briefly discussed under the definite example of ${\Lambda }_b\to {\Lambda }_c$ decay.

Comments: 11 pages in REVTeX, no figures