Search for the charmonium weak decay $\psi (2S)\to D_s^{-}{\pi }^{+}+c\mathrm{.}c\mathrm{.}$ and $\psi (2S)\to D_s^{-}{\rho }^{+}+c\mathrm{.}c\mathrm{.}$

We search for the weak decays $\psi (2S)\to D_s^{-}{\pi }^{+}+c\mathrm{.}c\mathrm{.}$ and $\psi (2S)\to D_s^{-}{\rho }^{+}+c\mathrm{.}c\mathrm{.}$ for the first time. The search is based on $(2712.4\pm 14.3)\times {10}^6$ events containing the charmonium state $\psi (2S)$ collected at the center-of-mass energy $\sqrt{s}=3.686\mathrm{G}\mathrm{e}\mathrm{V}$ with the BESIII detector. This search offers a unique opportunity to test the Standard Model and search for new physics. Since no signal excess above the background is observed, the upper limits on the branching fractions at the 90% confidence level are set to be $1.4\times {10}^{-6}$ and $7.0\times {10}^{-6}$ for $\psi (2S)\to D_s^{-}{\pi }^{+}+c\mathrm{.}c\mathrm{.}$ and $\psi (2S)\to D_s^{-}{\rho }^{+}+c\mathrm{.}c\mathrm{.}$, respectively.