Observation of $D_s (2317)^+ \to D_s^* \gamma$ at Belle and Belle II

Abstract We observe the radiative decay $D^{*}_{s0}(2317)^{+} \to D_{s}^{*+} \gamma$ 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~$\rm fb^{-1}$ and 427.9~$\rm fb^{-1}$ collected by the Belle and Belle~II detectors operating at the KEKB and SuperKEKB asymmetric-energy $e^+e^-$ colliders, respectively. The branching fraction ratio ${\cal B}(D^{*}_{s0}(2317)^{+} \to D_{s}^{*+} \gamma)/{\cal B}(D^{*}_{s0}(2317)^{+} \to D_{s}^{+} \pi^{0})$ is measured to be $[7.14 \pm 0.70({\rm stat.}) \pm 0.23({\rm syst.})]\%$. This result provides significant new experimental input for the determination of the quark structure of the $D^{*}_{s0}(2317)^{+}$, which remains unknown.
Tags Belle Run 1
Working group Charm
Principal authors @  Yubo Li, Chengping Shen
Reference submitted to PRL
Links arXiv:2510.27174, Inspire,
Bibtex 
@article{Belle-II:2025dzk,
    author = "Abumusabh, M. and others",
    collaboration = "Belle-II",
    title = "{Observation of the radiative decay $D_s (2317)^+ \to D_s^* γ$}",
    eprint = "2510.27174",
    archivePrefix = "arXiv",
    primaryClass = "hep-ex",
    reportNumber = "Belle II Preprint {\#}2025-026? KEK Preprint {\#}2025-28",
    month = "10",
    year = "2025"
}