Measurements of $\hat{I}\pounds$ electromagnetic form factors in the time-like region using the untagged initial-state radiation technique

Abstract

The process $e^{+}{e}^{-}\to \hat{I}{\pounds }^{+}\bar{\hat{I}}{\pounds }^{-}$ is studied from threshold up to 3.04 GeV/$c^2$ via the initial-state radiation technique using data with an integrated luminosity of 12.0 fb${}^{-1}$, collected at center-of-mass energies between 3.773 and 4.258 GeV with the BESIII detector at the BEPCII collider. The pair production cross sections and the effective form factors of $\hat{I}\pounds$ are measured in eleven $\hat{I}{\pounds }^{+}\bar{\hat{I}}{\pounds }^{-}$ invariant mass intervals from threshold to 3.04 GeV/$c^2$. The results are consistent with the previous results from Belle and BESIII. Furthermore, the branching fractions of the decays $J/\ddot{I}ˆ\to \hat{I}{\pounds }^{+}\bar{\hat{I}}{\pounds }^{-}$ and $\ddot{I}ˆ(3686)\to \hat{I}{\pounds }^{+}\bar{\hat{I}}{\pounds }^{-}$ are determined and the obtained results are consistent with the previous results of BESIII.

13 pages, 6 figures