Measurement of two-photon decay width of $\ddot{I}{‡}_{c2}(1P)$ in ${\hat{I}}^3{\hat{I}}^3\to \ddot{I}{‡}_{c2}(1P)\to J/\ddot{I}ˆ{\hat{I}}^3$ at Belle

Abstract

We report the measurement of the two-photon decay width of $\ddot{I}{‡}_{c2}(1P)$ in two-photon processes at the Belle experiment. We analyze the process ${\hat{I}}^3{\hat{I}}^3\to \ddot{I}{‡}_{c2}(1P)\to J/\ddot{I}ˆ{\hat{I}}^3$, $J/\ddot{I}ˆ\to {\ell }^{+}{\ell }^{-}$ $(\ell =e\mathrm{or}\hat{I}¼)$ using a data sample of 971 fb${}^{-1}$ collected with the Belle detector at the KEKB $e^{+}{e}^{-}$ collider. In this analysis, the product of the two-photon decay width of $\ddot{I}{‡}_{c2}(1P)$ and the branching fraction is determined to be $\hat{I}{“}_{{\hat{I}}^3{\hat{I}}^3}(\ddot{I}{‡}_{c2}(1P))\mathcal{B}(\ddot{I}{‡}_{c2}(1P)\to J/\ddot{I}ˆ{\hat{I}}^3)\mathcal{B}(J/\ddot{I}ˆ\to {\ell }^{+}{\ell }^{-})=14.8$ $\pm$ $0.3(stat.)$ $\pm$ $0.7(syst.)$ eV, which corresponds to $\hat{I}{“}_{{\hat{I}}^3{\hat{I}}^3}(\ddot{I}{‡}_{c2}(1P))$ = 653 $\pm$ 13(stat.) $\pm$ 31(syst.) $\pm$ 17(B.R.) eV, where the third uncertainty is from $\mathcal{B}(\ddot{I}{‡}_{c2}(1P)\to J/\ddot{I}ˆ{\hat{I}}^3)$ and $\mathcal{B}(J/\ddot{I}ˆ\to {\ell }^{+}{\ell }^{-})$.