# Observation of $\psi(3686)\rightarrow\Xi(1530)^{-}\bar\Xi(1530)^{+}$ and $\Xi(1530)^{-}\bar\Xi^{+}$

## TL;DR

This paper reports the first observation of specific decay modes of the $oldsymbol{\psi(3686)}$ particle into baryon-antibaryon pairs, measuring their branching fractions and angular distribution parameters with high statistical significance.

## Contribution

It presents the first observation and measurement of branching fractions for $oldsymbol{\psi(3686)}$ decays into $oldsymbol{\Xi(1530)}$ baryon pairs using a large data sample and a novel single-baryon tagging technique.

## Key findings

- First observation of $oldsymbol{\psi(3686)}$ decays to $oldsymbol{\Xi(1530)}$ pairs.
- Measured branching fractions: (11.45 ± 0.40 ± 0.59)×10^{-5} and (0.70 ± 0.11 ± 0.04)×10^{-5}.
- Angular distribution parameter $oldsymbol{\alpha}$ = 0.40 ± 0.24 ± 0.06, consistent with theoretical predictions.

## Abstract

Using 448.1 $\times$ $10^{6}$ $\psi(3686)$ events collected with the BESIII detector at BEPCII, we employ a single-baryon tagging technique to make the first observation of $\psi(3686)\rightarrow\Xi(1530)^{-}\bar\Xi(1530)^{+}$ and $\Xi(1530)^{-}\bar\Xi^{+}$ decays with a statistical significance of more than 10$\sigma$ and 5.0$\sigma$, respectively. The branching fractions are measured to be $\cal{B}$$[\psi(3686)\rightarrow\Xi(1530)^{-}\bar\Xi(1530)^{+}] $ = (11.45 $\pm$ 0.40 $\pm$ 0.59) $\times$ $10^{-5}$ and $\cal{B}$$[\psi(3686)\rightarrow\Xi(1530)^{-}\bar\Xi^{+}]$ = (0.70 $\pm$ 0.11 $\pm$ 0.04) $\times$ $10^{-5}$. The angular distribution parameter for $\psi(3686)\rightarrow\Xi(1530)^{-}\bar\Xi(1530)^{+}$ is determined to be $\alpha$ = 0.40 $\pm$ 0.24 $\pm$ 0.06, which agrees with the theoretical predictions within 1$\sigma$. The first uncertainties are statistical, and the second systematic.