Measurement of $\hat{I}›$ transverse polarization in $e^{+}{e}^{-}$ collisions at $\sqrt{s}=3.68-3.71$ GeV

Abstract

With data samples collected with the BESIII detector at seven energy points at $\sqrt{s}=3.68-3.71$ GeV, corresponding to an integrated luminosity of 333 pb${}^{-1}$, we present a study of the $\hat{I}›$ transverse polarization in the $e^{+}{e}^{-}\to \hat{I}›\bar{\hat{I}}›$ reaction. The significance of polarization by combining the seven energy points is found to be 2.6$\ddot{I}ƒ$ including the systematic uncertainty, which implies a non-zero phase between the transition amplitudes of the $\hat{I}›\bar{\hat{I}}›$ helicity states. The modulus ratio and the relative phase of EM-$psionic$ form factors combined with all energy points are measured to be $R^{\hat{I}}¨=$ 0.71${}_{-0.10}^{+0.10}$ $\pm$ 0.03 and $\hat{I}”\hat{I}{¦}^{\hat{I}}¨$ = (23${}_{-8.0}^{+8.8}$ $\pm$ 1.6${)}^{\circ }$, where the first uncertainties are statistical and the second systematic.

19 pages, 4 figures, 3 tables, consistent with the publication in JHEP10(2023)081 and JHEP12(2023)080 (erratum)