Observation of $\hat{I}ž(1530{)}^0$ Polarization and Determination of Its Electric and Magnetic Moments in $\ddot{I}ˆ(3686)\to \hat{I}ž(1530{)}^0\bar{\hat{I}}ž(1530{)}^0$

Abstract

Using the data sample of $2.7\times 10^9$ $\ddot{I}ˆ(3686)$ events collected with the BESIII detector at the BEPCII collider, we present an observation of the $\hat{I}ž(1530{)}^0$ polarization in the decay $\ddot{I}ˆ(3686)\to \hat{I}ž(1530{)}^0\bar{\hat{I}}ž(1530{)}^0$ with a significance larger than $20\ddot{I}ƒ$ compared with all other tested hypotheses. The helicity amplitudes for the process $\ddot{I}ˆ(3686)\to \hat{I}ž(1530{)}^0\bar{\hat{I}}ž(1530{)}^0$ 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 $\hat{I}ž(1530{)}^0$ and $\bar{\hat{I}}ž(1530{)}^0$ are measured.

10 pages, 4 figures, consistent with the publication in Physical Review Letters