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  • Ablikim, M; Achasov, M. N; Bertani, M; Bettoni, D; Briere, R. A; Chen, C; Chen, M. L; Chen, X. T; Chen, Z. J; Cui, J. J; Dai, J. P; Denig, A; Ding, B; Ding, Y; Dong, X; Du, S. X; Fan, Y. H; Fang, Y; Feng, Y. T; Ge, Z. W; Guan, Z. L; Holtmann, T; Hou, Z. L; Huang, G. S; Hüsken, N; Ji, Q. P; Ji, W; Ji, X. B; Jiang, D; Jiang, H. B; Jiang, P. C; Jing, M. Q; Johansson, T; Kabana, S; Khachatryan, V; Khoukaz, A; Kiuchi, R; Li, F; Li, H. N; Li, L. K; Li, Xiaoyu; Liao, G. R; Liao, Y. P; Lin, T; Liu, B. J; Liu, B. X; Liu, Huanhuan; Liu, K; Liu, M. H; Liu, Z. D; Lu, Y. P; Luo, T; Lyu, X. R; Ma, F. C; Ma, R. Q; Mao, Y. J; Niu, Q. L; Pelizaeus, M; Peng, Y. Y; Prasad, V; Qian, S; Qian, W. B; Rong, G; Shao, L. G; Shao, M; Shen, C. P; Shen, H. F; Shi, B. A; Shi, Q. Q; Shi, R. S; Shi, S. Y; Song, T. Z; Sun, G. B; Sun, Y. J; Tang, G. Y; Tian, Z. F; Wang, D. Y; Wang, M; Wang, Y; Wen, S. P; Wu, L. J; Wu, Y. H; Xian, X. M; Xiao, Y. L; Xie, Z. P; Xu, C. F; Xu, Z. S; Zeng, Y. J; Zhan, Y. H; Zhang, D. H; Zhang, J. Y; Zhao, J. Y; Zhao, Lei; Zhao, Y. X; Zhemchugov, A; Zheng, B; Zheng, J. P; Zhou, X. R; Zhou, X. Y; Zhu, Z. A

    04/2024
    Journal Article

    Using 7.33~fb$^{-1}$ of $e^{+}e^{-}$ collision data collected by the BESIII detector at center-of-mass energies in the range of $\sqrt{s}=4.128 - 4.226$~GeV, we search for the rare decays $D_{s}^+\to h^+(h^{0})e^{+}e^{-}$, where $h$ represents a kaon or pion. By requiring the $e^{+}e^{-}$ invariant mass to be consistent with a $\phi(1020)$, $0.98<M(e^{+}e^{-})<1.04$ ~GeV/$c^2$, the decay $D_s^+\to\pi^+\phi,\phi\to e^{+}e^{-}$ is observed with a statistical significance of 7.8$\sigma$, and evidence for the decay $D_s^+\to\rho^+\phi,\phi\to e^{+}e^{-}$ is found for the first time with a statistical significance of 4.4$\sigma$. The decay branching fractions are measured to be $\mathcal{B}(D_s^+\to\pi^+\phi, \phi\to e^{+}e^{-} )=(1.17^{+0.23}_{-0.21}\pm0.03)\times 10^{-5}$, and $\mathcal{B}(D_s^+\to\rho^+\phi, \phi\to e^{+}e^{-} )=(2.44^{+0.67}_{-0.62}\pm 0.16)\times 10^{-5}$, where the first uncertainties are statistical and the second systematic. No significant signal for the three four-body decays of $D_{s}^{+}\to \pi^{+}\pi^{0}e^{+}e^{-},\ D_{s}^{+}\to K^{+}\pi^{0}e^{+}e^{-}$, and $D_{s}^{+}\to K_{S}^{0}\pi^{+}e^{+}e^{-}$ is observed. For $D_{s}^{+}\to \pi^{+}\pi^{0}e^{+}e^{-}$, the $\phi$ mass region is vetoed to minimize the long-distance effects. The 90$\%$ confidence level upper limits set on the branching fractions of these decays are in the range of $(7.0-8.1)\times 10^{-5}$.