Determination of the $\Lambda_c^+$ spin via the reaction $e^+e^-\to\Lambda_c^+\bar\Lambda_c^-$

TL;DR

This study determines the spin of the $\\Lambda_c^+$ baryon as $J=\frac{1}{2}$ by analyzing angular distributions in $e^+e^-\to\Lambda_c^+\bar\Lambda_c^-$ events recorded at 4.6 GeV, providing a definitive spin assignment with high significance.

Contribution

The paper provides the first high-significance experimental confirmation of the $\\Lambda_c^+$ baryon's spin as $J=\frac{1}{2}$ using angular distribution analysis.

Findings

The $\\Lambda_c^+$ has spin $J=\frac{1}{2}$ with over 6 sigma significance.

Angular distributions favor the $J=\frac{1}{2}$ hypothesis.

Data collected at 4.6 GeV with the BESIII detector supports the spin determination.

Abstract

We report on a comparison of two possible $\Lambda_c^+$ spin hypotheses, $J=\frac{1}{2}$ and $\frac{3}{2}$, via the process $e^+e^-\to\Lambda_c^+\bar\Lambda_c^-$, using the angular distributions of $\Lambda_c^+$ decays into $pK_S^0$, $\Lambda\pi^+$, $\Sigma^0\pi^+$, and $\Sigma^+\pi^0$. The data were recorded at $\sqrt s = 4.6$ GeV with the BESIII detector and correspond to an integrated luminosity of 587 pb$^{-1}$. The $\Lambda_c^+$ spin is determined to be $J=\frac{1}{2}$, with this value favored over the $\frac{3}{2}$ hypothesis with a significance corresponding to more than 6 Gaussian standard deviations.