Study of the near-threshold $\ddot{I}‰\ddot{I}•$ mass enhancement in doubly OZI suppressed $J/\ddot{I}ˆ\to {\hat{I}}^3\ddot{I}‰\ddot{I}•$ decays

Abstract

A 2.25$\times 10^8$ $\jpsi$ event sample accumulated with the BESIII detector is used to study the doubly OZI suppressed decay modes $\jpsi\toγ\of$, $ω\to\ppp$, $ϕ\to\kk$. A strong deviation ($>$ 30$\ddot{I}ƒ$) from three-body $\jpsi\toγωϕ$ phase space is observed near the $\ddot{I}‰\ddot{I}•$ mass threshold that is consistent with a previous observation reported by the BESII experiment. A partial wave analysis with a tensor covariant amplitude that assumes that the enhancement is due to the presence of a resonance, the X(1810), is performed, and confirms that the spin-parity of the X(1810) is $0^{++}$. The mass and width of the X(1810) are determined to be $M=1795\pm 7$(stat)${}_{-5}^{+13}$(syst)$\pm$19(mod) MeV/$c^2$ and $\hat{I}“=95\pm 10$(stat)${}_{-34}^{+21}$(syst)$\pm$75(mod) MeV/$c^2$, respectively, and the product branching fraction is measured to be ${\cal B}(\jpsi\toγX(1810))\times{\cal B}(X(1810)\to\of)=(2.00\pm0.08$(stat)${}_{-1.00}^{+0.45}$(syst)$\pm$1.30(mod))$\times 10^{-4}$. %where the first error is the statistical error and the second the systematical error. These results are consistent within errors with those of the BESII experiment.