Search for an isoscalar partner of the $Z_c(3900)$ in $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\hat{I}\cdot J/\ddot{I}ˆ$

Abstract

Using a data sample corresponding to an integrated luminosity of 20.3 fb${}^{-1}$ collected at center-of-mass energies from 4.18 to 4.95 GeV with the BESIII detector, we observe the process $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\hat{I}\cdot J/\ddot{I}ˆ$ with a statistical significance of $6.0\ddot{I}ƒ$, including systematic uncertainties. The isoscalar partner of the $Z_c(3900)$, denoted $X(3900)$, is searched for in the $\hat{I}\cdot J/\ddot{I}ˆ$ final state, and no significant signal is observed. The upper limits on the product of the Born cross section $\ddot{I}{ƒ}^{\mathrm{Born}}[e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}X(3900)$] and the branching fraction $\mathcal{B}[X(3900)\to \hat{I}\cdot J/\ddot{I}ˆ]$ are given with various assumptions for the mass and width of the $X(3900)$.

13 pages, 4 figures