Charmed Baryon Lambda Subscript C Decays With A Sigma In The Final State And Decay Asymmetry Parameters

Charmed baryon [lambda][subscript]c+ decays with a [sigma]+ in the final state and decay asymmetry parameters

A Study of the Decay Properties of the Charmed Baryon Charmed Positive Lambda Baryon

The charmed baryon $\Lambda\sbsp{c}{+}$ has been observed using the ARGUS detector in the DORIS II $e\sp{+}e\sp-$ storage ring at DESY. The ARGUS experiment is a 4$\pi$ magnetic solenoidal detector used to observe $e\sp{+}e\sp-$ annihilations at center-of-mass energies around 10.4 GeV. We have studied 5 decays modes of the $\Lambda\sbsp{c}{+}$. The decay mode $\Lambda\sbsp{c}{+}\to pK\sp-\pi\sp+$ was used to measure the $\Lambda\sbsp{c}{+}$ fragmentation properties. A value of 0.24 $\pm$ 0.04 was found for the Peterson et al. parameter $\epsilon$, and the $\sigma(\Lambda\sbsp{c}{+}$) $\cdot\ BR(\Lambda\sbsp{c}{+}\to pK\sp-\pi\sp+$) was measured to be 12.0 $\pm$ 1.1 $\pm$ 1.3) pb. The decay modes $\Lambda\sbsp{c}{+}\to\Lambda\pi\sp+$ and $\Lambda\sbsp{c}{+}\to\Sigma\sp0\pi\sp+$ were also studied. In the former the asymmetry parameter $\alpha\sb{\Lambda\sb{c}}$ was measured to be $-$1.0 $\pm$ 0.5, indicating that parity is maximally violated in this decay. The two production cross section times branching ratios were measured to be (2.2 $\pm$ 0.3 $\pm$ 0.3) pb and (2.0 $\pm$ 0.7 $\pm$ 0.3) pb respectively. Finally, a search was made for evidence of W-exchange in the decay $\Lambda\sbsp{c}{+}\to\Xi\sp-K\sp+\pi\sp+$. This final state can arise through a simple spectator decay or via the more exotic W-exchange decay into $\Xi\sp{*0}K\sp+$, where the $\Xi\sp{*0}$ subsequently decays into $\Xi\sp-\pi\sp+$. The two body rate was measured to be (35 $\pm$ 17)% of the three body rate, indicating that a significant portion of the $\Xi\sp-K\sp+\pi\sp+$ final state may occur via W-exchange.

Observation of Two Excited Charmed Baryons Decaying Into Lambda(c)+ Pi+-

Using data recorded by the CLEO-II detector at CESR, we report evidence of a pair of excited charmed baryons, one decaying into[Lambda][sub c][sup+][pi][sup+] and the other into[Lambda][sub c][sup+][pi][sup -]. The doubly charged state has a measured mass difference M([Lambda][sub c][sup+][pi][sup+]) - M([Lambda][sub c][sup+]) of 234.5[+-] 1.1[+-] 0.8 MeV and a width of 17.9[sub -3.2][sup+3.8][+-] 4.0 MeV, and the neutral state has a measured mass difference M([Lambda][sub c][sup+][pi][sup -]) - M([Lambda][sub c][sup+]) of 232.6[+-] 1.0[+-] 0.8 MeV and a width of 13.0[sub -3.0][sup+3.7][+-] 4.0 MeV. We identify these states as[Sigma]*[sub c][sup++] and[Sigma]*[sub c][sup 0], the spin 3/2[sup+] excitations of the[Sigma][sub c] baryons.