Model independent determination of the spin of the $\Omega^{-}$ and its polarization alignment in $\psi(3686)\rightarrow\Omega^{-}\bar{\Omega}^{+}$

TL;DR

This paper measures the spin and polarization of the Omega-minus baryon in a specific decay process, using a large data set, and provides the first measurement of helicity amplitudes and decay parameters with improved precision.

Contribution

It introduces a model-independent method to determine the Omega-minus spin and polarization in the decay process, with the first measurement of helicity amplitudes and decay parameters.

Findings

Branching fraction of $ o ext{Omega}^- ar{ ext{Omega}}^+$ measured as $(5.82 extpm 0.12 extpm 0.24) imes 10^{-5}$

Helicity amplitudes and decay parameters for the first time measured

Enhanced precision over previous measurements

Abstract

We present an analysis of the process $\psi(3686) \to \Omega^- \bar{\Omega}^+$ ($\Omega^-\to K^-\Lambda$, $\bar{\Omega}^+\to K^+\bar{\Lambda}$, $\Lambda\to p\pi^-$, $\bar{\Lambda}\to \bar{p}\pi^+$) based on a data set of $448\times 10^6$ $\psi(3686)$ decays collected with the BESIII detector at the BEPCII electron-positron collider. The helicity amplitudes for the process $\psi(3686) \to \Omega^- \bar{\Omega}^+$ and the decay parameters of the subsequent decay $\Omega^-\to K^-\Lambda$ $(\bar{\Omega}^+\to K^+\bar{\Lambda})$ are measured for the first time by a fit to the angular distribution of the complete decay chain. The branching fraction of $\psi(3686) \to \Omega^- \bar{\Omega}^+$ is measured to be $(5.82\pm 0.12\pm 0.24)\times 10^{-5}$, with an improved precision compared to previous measurements.