Observation of $h_c$ radiative decay $h_c\to {\hat{I}}^3\hat{I}{\cdot }^{\prime }$ and evidence for $h_c\to {\hat{I}}^3\hat{I}\cdot$

Abstract

A search for radiative decays of the $P$-wave spin singlet charmonium resonance $h_c$ is performed based on $4.48\times 10^8$ $\ddot{I}{ˆ}^{\prime }$ events collected with the BESIII detector operating at the BEPCII storage ring. Events of the reaction channels $h_c\to {\hat{I}}^3\hat{I}{\cdot }^{\prime }$ and ${\hat{I}}^3\hat{I}\cdot$ are observed with a statistical significance of $8.4\ddot{I}ƒ$ and $4.0\ddot{I}ƒ$, respectively, for the first time. The branching fractions of $h_c\to {\hat{I}}^3\hat{I}{\cdot }^{\prime }$ and $h_c\to {\hat{I}}^3\hat{I}\cdot$ are measured to be $\mathcal{B}(h_c\to {\hat{I}}^3\hat{I}{\cdot }^{\prime })=(1.52\pm 0.27\pm 0.29)\times 10^{-3}$ and $\mathcal{B}(h_c\to {\hat{I}}^3\hat{I}\cdot )=(4.7\pm 1.5\pm 1.4)\times 10^{-4}$, respectively, where the first errors are statistical and the second are systematic uncertainties.

7 pages, 2 figures