Observation of the decay $X(3872)\to \ddot{I}{€}^0\ddot{I}{‡}_{c1}(1P)$

Abstract

Using a total of $9.0{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data with center-of-mass energies between 4.15 and 4.30 GeV collected by the BESIII detector, we search for the processes $e^{+}{e}^{-}\to {\hat{I}}^{3}X(3872)$ with $X(3872)\to \ddot{I}{€}^0\ddot{I}{‡}_{cJ}$ for $J=0,1,2$. We report the first observation of $X(3872)\to \ddot{I}{€}^0\ddot{I}{‡}_{c1}$, a new decay mode of the $X(3872)$, with a statistical significance of more than 5$\ddot{I}ƒ$. Normalizing to the previously established process $e^{+}{e}^{-}\to {\hat{I}}^{3}X(3872)$ with $X(3872)\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}J/\ddot{I}ˆ$, we find $\mathcal{B}(X(3872)\to \ddot{I}{€}^0\ddot{I}{‡}_{c1})/\mathcal{B}(X(3872)\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}J/\ddot{I}ˆ)=0.88_{-0.27}^{+0.33}\pm 0.10$, where the first error is statistical and the second is systematic. We set 90% confidence level upper limits on the corresponding ratios for the decays to $\ddot{I}{€}^0\ddot{I}{‡}_{c0}$ and $\ddot{I}{€}^0\ddot{I}{‡}_{c2}$ of 19 and 1.1, respectively.

8 pages, 4 figures