Cabibbo-allowed nonleptonic weak decays of charmed baryons

Abstract

Cabibbo-allowed nonleptonic weak decays of charmed baryons ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}^{+}$, ${\mathrm{\ensuremath{\Xi}}}_{\mathit{c}}^{0\mathit{A}}$, ${\mathrm{\ensuremath{\Xi}}}_{\mathit{c}}^{+\mathit{A}}$, and ${\mathrm{\ensuremath{\Omega}}}_{\mathit{c}}^{0}$ into an octet baryon and a pseudoscalar meson are analyzed. The nonfactorizable contributions are evaluated under the pole approximation, and it turns out that the s-wave amplitudes are dominated by the low-lying 1/${2}^{\mathrm{\ensuremath{-}}}$ resonances, while p-wave ones are governed by the ground state 1/${2}^{+}$ poles. The MIT bag model is employed to calculate the coupling constants, form factors, and baryon matrix elements. Our conclusions are the following: (i) s waves are no longer dominated by commutator terms; the current-algebra method is not applicable to parity-violating amplitudes. (ii) Nonfactorizable W-exchange effects are generally important; they can be comparable to and sometimes even dominate over factorizable contributions, depending on the decay modes under consideration. (iii) The large-${\mathit{N}}_{\mathit{c}}$ approximation for factorizable amplitudes also works in the heavy baryon sector and it accounts for the color nonsuppression of ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}^{+}$\ensuremath{\rightarrow}pK${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}^{0}$ relative to ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}^{+}$\ensuremath{\rightarrow}\ensuremath{\Lambda}${\mathrm{\ensuremath{\pi}}}^{+}$. (iv) A measurement of the decay rate and the sign of the \ensuremath{\alpha} asymmetry parameter of certain proposed decay modes will help discern various models. (v) p waves are the dominant contributions to the decays ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}^{+}$\ensuremath{\rightarrow}${\mathrm{\ensuremath{\Xi}}}^{0}$${\mathit{K}}^{+}$ and ${\mathrm{\ensuremath{\Xi}}}_{\mathit{c}}^{0\mathit{A}}$\ensuremath{\rightarrow}${\mathrm{\ensuremath{\Sigma}}}^{+}$${\mathit{K}}^{\mathrm{\ensuremath{-}}}$, but they are subject to a large cancellation; this renders present theoretical predictions on these two channels unreliable.