Evidence for the semileptonic decays $\Lambda_c^{+} \to \Sigma^{\pm} \pi^{\mp} e^+ \nu_e$

TL;DR

This study reports the first evidence for semileptonic decays of the Lambda_c+ baryon into Sigma pi e nu final states, measuring their branching fraction using data from the BESIII detector.

Contribution

First experimental evidence for Lambda_c+ to Sigma pi e nu decays, with a measured branching fraction consistent with theoretical predictions.

Findings

Evidence with 3.6 sigma significance for the decay.

Measured branching fraction of approximately 7.7 x 10^{-4}.

Results align with quark model predictions within two standard deviations.

Abstract

Using $4.5\, fb^{-1}$ of $e^+e^-$ collision data collected by the BESIII detector at center-of-mass energies between $4.600$ and $4.699\,GeV$, we search for the semileptonic decays $\Lambda_c^{+} \to \Sigma^{+} \pi^{-} e^+ \nu_e$ and $\Lambda_c^{+} \to \Sigma^{-} \pi^{+} e^+ \nu_e$ for the first time. Assuming their branching fractions are equal under isospin symmetry, evidence for $\Lambda_c^{+} \to \Sigma^{\pm} \pi^{\mp} e^+ \nu_e$ is reported with a significance of $3.6\sigma$. The corresponding branching fraction is measured to be $\mathcal{B}(\Lambda_c^{+} \to \Sigma^\pm\pi^\mp e^+\nu_e) = (7.7^{+2.5}_{-2.3_{\rm stat.}}\pm1.3_{\rm syst.})\times 10^{-4}$, which is consistent with quark model predictions within two standard deviations.