Measurement of cross section for $e^{+}{e}^{-}\to \hat{I}{ž}^0\bar{\hat{I}}{ž}^0$ near threshold

Abstract

Using $e^{+}{e}^{-}$ collision data at ten center-of-mass energies between 2.644 and 3.080 GeV collected with the BESIII detector at BEPCII and corresponding to an integrated luminosity of about 500 pb${}^{-1}$, we measure the cross sections and effective form factors for the process $e^{+}{e}^{-}\to \hat{I}{ž}^0\bar{\hat{I}}{ž}^0$ utilizing a single-tag method. A fit to the cross section of $e^{+}{e}^{-}\to \hat{I}{ž}^0\bar{\hat{I}}{ž}^0$ with a pQCD-driven power function is performed, from which no significant resonance or threshold enhancement is observed. In addition, the ratio of cross sections for the processes $e^{+}{e}^{-}\to \hat{I}{ž}^{-}\bar{\hat{I}}{ž}^{+}$ and $\hat{I}{ž}^0\bar{\hat{I}}{ž}^0$ is calculated using recent BESIII measurement and is found to be compatible with expectation from isospin symmetry.

11 pages, 5 figures. Consistent with paper published in Phys. Lett. B 820 (2021) 136557