Measurement of branching fractions of $Λ_{c}^{+}$ decays to $Σ^{+} η$ and $Σ^{+} η'$

TL;DR

This work presents precise measurements of the branching-fraction ratios for Λc+ decays to Σ+ η and Σ+ η′ using 4.5 fb^-1 of e+e− collision data collected with the BESIII detector. A single-tag technique is used, and a simultaneous unbinned maximum-likelihood fit to the beam-constrained mass distributions across seven energy points yields BF ratios of 0.305(stat)±0.007(syst) for Σ+ η and 0.336(stat)±0.037(syst) for Σ+ η′, with a BF(Σ+ η′)/BF(Σ+ η) = 1.73(stat)±0.16(syst). The η′ channel has a significance of 4.1σ, while the η channel reaches 8.4σ, indicating clear signals and improved precision over prior results. The measurements help discriminate among theoretical approaches to charmed-baryon decays, particularly those involving nonfactorizable W-emission and SU(3) flavor-symmetry considerations, and they offer important benchmarks for future study of CF decays in heavy baryons.

Abstract

By analyzing $e^+e^-$ collision data taken at center-of-mass energies $\sqrt{s}$ between 4.600 and 4.699 GeV with the BESIII detector at the BEPCII collider, corresponding to an integrated luminosity of $\rm 4.5~fb^{-1}$, we study the hadronic decays $Λ_{c}^{+} \rightarrow Σ^{+} η$ and $Λ_{c}^{+} \rightarrow Σ^{+} η^{\prime}$ using the single-tag method. The branching fraction ratio of $Λ_{c}^+ \rightarrow Σ^+ η$ relative to $Λ_{c}^+ \rightarrow Σ^+ π^0$ is determined to be $0.305 \pm 0.046_{\rm stat.} \pm 0.007_{\rm syst.}$, and that of $Λ_{c}^+ \rightarrow Σ^+ η'$ relative to $Λ_{c}^+ \rightarrow Σ^+ ω$ is $0.336 \pm 0.094_{\rm stat.} \pm 0.037_{\rm syst.}$. The ratio of $\frac{\mathcal{B}\left(Λ_{c}^{+} \rightarrow Σ^{+} η'\right)}{\mathcal{B}\left(Λ_{c}^{+} \rightarrow Σ^{+} η\right)} $ is determined to be $1.73 \pm 0.22_{\rm stat.} \pm 0.16_{\rm syst.}$. These results enrich our knowledge of charmed baryon decays.

Figures (3)

• Figure 1: Feynman diagrams of the $\Lambda_{c}^+ \rightarrow \Sigma^+ \eta/\eta'$ decay.
• Figure 2: Distributions of $M_{\rm BC}$ of accepted candidates for each decay, combined from all energy points. The MC samples have been scaled to that of data. The black dots with error bars are data combining all energy points, the red lines show the signal, the green histograms represent the $\Lambda_c\bar{\Lambda}_c$ backgrounds, and the yellow histograms represent the other backgounds.
• Figure 3: Projections of the simultaneous fit to the $M_{\rm BC}$ distributions at different energy points for each decay mode. The black dots with error bars are data combining all energy points, the green lines show the signal, the dashed blue lines represent the background, and the red lines are the sum of the fit functions.