Search for the charmonium weak decay $ψ(2S)\to D_s^-π^+ + c.c.$ and $ψ(2S)\to D_s^-ρ^+ + c.c.$

Abstract

We search for the weak decays $ψ(2S)\to D_s^-π^+ + c.c.$ and $ψ(2S)\to D_s^-ρ^+ + c.c.$ for the first time. The search is based on $(2712.4\pm14.3)\times 10^6$ events containing the charmonium state $ψ(2S)$ collected at the center-of-mass energy $\sqrt{s}=3.686\ \rm{GeV}$ 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 $ψ(2S)\to D_s^-π^+ + c.c.$ and $ψ(2S)\to D_s^-ρ^+ + c.c.$, respectively.

Figures (3)

• Figure 1: The Feynman diagram of $\psi(2S)\to D_s^-\pi^+$ and $\psi(2S)\to D_s^-\rho^+$ at tree-level.
• Figure 2: The invariant mass distributions $M_{D_s^-}$ for the decay channels (a) $\psi(2S)\to D_s^-\pi^+$ and (b) $\psi(2S)\to D_s^-\rho^+$. The black dots with error bars are data; while the blue and red lines are the signal and inclusive MC samples, respectively. The signal MC distributions have been scaled to the calculated upper limits of BFs. The magenta arrows indicate the defined signal regions.
• Figure 3: The distributions of normalized likelihoods for (a) $\psi(2S)\to D_s^-\pi^+$ and (b) $\psi(2S)\to D_s^-\rho^+$. The red arrows mark the upper limits of BFs at the 90% C.L..