Observation of Polarization and Determination of Electric and Magnetic Moments of $\Xi(1530)^0$ in $\psi(3686)\to\Xi(1530)^0\bar\Xi(1530)^0$

TL;DR

This study reports the first observation of polarization in the decay of $oldsymbol{\psi(3686) o ext{ extmu}Xi(1530)^0ar extmu}Xi(1530)^0$ and measures related helicity amplitudes and form factors, providing new insights into baryon structure.

Contribution

It is the first measurement of $oldsymbol{ ext{ extmu}Xi(1530)^0}$ polarization and form factors in $oldsymbol{ ext{ extmu} o ext{ extmu}Xi(1530)^0ar extmu}Xi(1530)^0$ decay.

Findings

Polarization observed with significance >20σ.

First measurement of helicity amplitudes and form factors.

Polarization correlations between $ ext{ extmu}Xi(1530)^0$ and $ar extmu}Xi(1530)^0$ are quantified.

Abstract

Using the data sample of $2.7\times10^9$ $\psi(3686)$ events collected with the BESIII detector at the BEPCII collider, we present an observation of the $\Xi(1530)^0$ polarization in the decay $\psi(3686)\to\Xi(1530)^0\bar\Xi(1530)^0$ with a significance larger than $20\sigma$ compared with all other tested hypotheses. The helicity amplitudes for the process $\psi(3686)\to\Xi(1530)^0\bar\Xi(1530)^0$ and the moduli of form factors including electric charge, magnetic dipole, electric quadrupole, and magnetic octupole are measured for the first time by performing an angular distribution analysis. Additionally, the polarization correlations between $\Xi(1530)^0$ and $\bar\Xi(1530)^0$ are measured.