Observation of the radiative decay $D_s(2317{)}^{+}\to D_s^{\ast }{\hat{I}}^3$

Abstract

We observe the radiative decay $D_{s0}^{\ast }(2317{)}^{+}\to D_s^{\ast +}{\hat{I}}^3$ for the first time, with a significance exceeding $10$ standard deviations. The signal is found in the continuum $e^{+}{e}^{-}\to c\bar{c}$ process with the combined data samples of 980.4~$\mathrm{f}{\mathrm{b}}^{-1}$ and 427.9~$\mathrm{f}{\mathrm{b}}^{-1}$ collected by the Belle and Belle~II detectors operating at the KEKB and SuperKEKB asymmetric-energy $e^{+}{e}^{-}$ colliders, respectively. The branching fraction ratio $\mathcal{B}(D_{s0}^{\ast }(2317{)}^{+}\to D_s^{\ast +}{\hat{I}}^3)/\mathcal{B}(D_{s0}^{\ast }(2317{)}^{+}\to D_s^{+}\ddot{I}{€}^0)$ is measured to be $[7.13\pm 0.70(stat.)\pm 0.23(syst.)]\%$. This result provides significant new experimental input for the determination of the quark structure of the $D_{s0}^{\ast }(2317{)}^{+}$, which remains unknown.

8 pages, 3 figures