Measurement of the branching fractions of the decays $Λ_{c}^{+}\rightarrowΛK_{S}^{0}K^{+}$, $Λ_{c}^{+}\rightarrowΛK_{S}^{0}π^{+}$ and $Λ_{c}^{+}\rightarrowΛK^{*+}$

TL;DR

Using 4.5 fb^{-1} of BESIII e^+e^- collision data near the Λ_c^+ Λ_c^- threshold, this work measures the branching fractions of Λ_c^+ → Λ K_S^0 K^+, Λ_c^+ → Λ K_S^0 π^+, and Λ_c^+ → Λ K^{*+}. The Λ_c^+ → Λ K_S^0 π^+ decay is observed for the first time with a significance of 8.9σ, and Λ_c^+ → Λ K^{*+} is established with 4.7σ significance under interference considerations between non-resonant and resonant components. The measured branching fractions are BF(Λ_c^+ → Λ K_S^0 K^+) = (3.04 ± 0.30 ± 0.16)×10^{-3}, BF(Λ_c^+ → Λ K_S^0 π^+) = (1.73 ± 0.27 ± 0.10)×10^{-3}, and BF(Λ_c^+ → Λ K^{*+}) depending on the interference phase θ_0 (e.g., (2.40 ± 0.58 ± 0.11)×10^{-3} with no interference, or higher values for certain θ_0). The results, which improve precision over previous measurements and show some deviations from SU(3) predictions, highlight the need for additional data and refined theoretical understanding of Λ_c^+ decays involving a Λ and strange hadrons.

Abstract

Studies are performed of the Cabibbo-favored decay $Λ_{c}^{+}\toΛK_{S}^{0}K^+$ and the singly Cabibbo-suppressed decay $Λ_{c}^{+}\toΛK_{S}^{0}π^+$, based on a sample of $e^{+}e^{-}$ collision data, corresponding to an integrated luminosity of 4.5 fb$^{-1}$, accumulated at center-of-mass energies between $4599.53$ MeV and $4698.82$ MeV with the BESIII detector. The decay $Λ_{c}^{+}\toΛK_{S}^{0}π^+$ is observed for the first time. The branching fractions of $Λ_{c}^{+}\toΛK_{S}^{0}K^+$ and $Λ_{c}^{+}\toΛK_{S}^{0}π^+$ are measured to be $(3.04\pm0.30\pm0.16)\times 10^{-3}$ and $(1.73\pm0.27\pm0.10)\times 10^{-3}$, respectively, where the first uncertainties are statistical and the second are systematic. These results correspond to the most precise measurement of these quantities for both decays. Evidence of a $K^{*+}$ contribution in the $Λ_{c}^{+}\toΛK_{S}^{0}π^+$ decay is found with a statistical significance of $4.7σ$. The branching fraction of $Λ_{c}^{+}\toΛK^{*+}$ is calculated under three possible interference scenarios.

Figures (9)

• Figure 1: Topology diagrams for $\Lambda_{c}^{+}\to \Lambda K_{S}^{0} K^{+}$.
• Figure 2: Topology diagrams for $\Lambda_{c}^{+}\to \Lambda K_{S}^{0} \pi^{+}$.
• Figure 3: Topology diagrams for $\Lambda_{c}^{+}\to \Lambda K^{*+}$.
• Figure 4: The 2-D simultaneous fit result projection on the $M_{\rm BC}$ and $M(p\pi^-)$ invariant-mass distributions of the $\Lambda_{c}^{+}\to\Lambda K_{S}^{0}K^+$ candidates in the $K_{S}^{0}$ signal (top row) and sideband (bottom row) regions.
• Figure 5: The one-dimensional fit to the $M(\pi^{+}\pi^{-})$ distribution for the $\Lambda_{c}^{+}\rightarrow \Lambda K_{S}^{0} K^{+}$ candidates. The red arrows indicate the signal region and the blue arrows indicate the sideband regions.