1/M corrections to baryonic form factors in the quark model.

Abstract

Weak current-induced baryonic form factors at zero recoil are evaluated in the rest frame of the heavy parent baryon using the nonrelativistic quark model. Contrary to previous similar work in the literature, our quark model results do satisfy the constraints imposed by heavy quark symmetry for heavy-heavy baryon transitions at the symmetric point v\ensuremath{\cdot}v\ensuremath{'}=1 and are in agreement with the predictions of the heavy quark effective theory for antitriplet-antitriplet heavy baryon form factors at zero recoil evaluated to order 1/${\mathit{m}}_{\mathit{Q}}$. Furthermore, the quark model approach has the merit that it is applicable to any heavy-heavy and heavy-light baryonic transitions at maximum ${\mathit{q}}^{2}$. Assuming a dipole ${\mathit{q}}^{2}$ behavior, we have applied the quark model form factors to nonleptonic, semileptonic, and weak radiative decays of the heavy baryons. It is emphasized that the flavor suppression factor occurring in many heavy-light baryonic transitions, which is unfortunately overlooked in most literature, is very crucial towards an agreement between theory and experiment for the semileptonic decay ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}$\ensuremath{\rightarrow}\ensuremath{\Lambda}${\mathit{e}}^{+}$${\ensuremath{\nu}}_{\mathit{e}}$. Predictions for the decay modes ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{b}}$\ensuremath{\rightarrow}J/\ensuremath{\psi}\ensuremath{\Lambda}, ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}$\ensuremath{\rightarrow}p\ensuremath{\varphi}, ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{b}}$\ensuremath{\rightarrow}\ensuremath{\Lambda}\ensuremath{\gamma}, ${\mathrm{\ensuremath{\Xi}}}_{\mathit{b}}$\ensuremath{\rightarrow}\ensuremath{\Xi}\ensuremath{\gamma}, and for the semileptonic decays of ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{b}}$, ${\mathrm{\ensuremath{\Xi}}}_{\mathit{b},}$c, and ${\mathrm{\ensuremath{\Omega}}}_{\mathit{b}}$ are presented. \textcopyright{} 1996 The American Physical Society.