Cabibbo-allowed nonleptonic weak decays of charmed baryons

Abstract

Cabibbo-allowed nonleptonic weak decays of charmed baryons $\lamc,~\xin,~\xip$ and $Ω_c^0$ into an octet baryon and a pseudoscalar meson are analyzed. The nonfactorizable contributions are evaluated under pole approximation, and it turns out that the $s$-wave amplitudes are dominated by the low-lying $\halfm$ resonances, while $p$-wave ones governed by the ground-state $\halfp$ poles. The MIT bag model is employed to calculate the coupling constants, form factors and baryon matrix elements. Our conclusions are: (i) $s$ waves are no longer dominated by commutator terms; the current-algebra method is certainly not applicable to parity-violating amplitudes, (ii) nonfactorizable $W$ exchange effects are generally important; they can be comparable to and somtimes even dominate over factorizable contributions, depending on the decay modes under consideration, (iii) large-$N_c$ approximation for factorizable amplitudes also works in the heavy baryon sector and it accounts for the color nonsuppression of $\lamc\ri p\bar{K}^0$ relative to $\lamc\riΛπ^+$, (iv) a measurement of the decay rate and the sign of the $α$ asymmetry parameter of certain proposed decay modes will help discern various models; especially the sign of $α$ in $\lamc\riΣπ$ decays can be used to unambiguously differentiate recent theoretical schemes from current algebra, and (v) $p$ waves are the dominant contributions to the decays $\lamc\riΞ^0 K^+$ and $\xin\riΣ^+ K^-$, but they are subject to a large cancellation; this renders present theoretical predictions on these two channels unreliable.