改进的 $\psi(3770) \to \gamma\eta_{c}(1S, 2S)$ 辐射跃迁搜索
Improved search for $ψ(3770) \to γη_{c}(1S, 2S)$ radiative transitions
AI总结：
利用BESIII在3.773 GeV处20.3 fb$^{-1}$数据改进搜索$\psi(3770)\to\gamma\eta_c(1S,2S)$，未发现显著信号，将分支比和宽度上限分别降低约三倍和两倍。
AI中文摘要：
基于BEPCII对撞机上BESIII探测器在质心能量3.773 GeV处收集的积分亮度为20.3 fb$^{-1}$的$e^{+}e^{-}$湮灭数据，利用强子衰变$\eta_{c}(1S, 2S) \to K^{0}_{S} K^{\pm} \pi^{\mp}$对辐射跃迁$\psi(3770) \to \gamma \eta_{c}(1S, 2S)$进行了改进的搜索。未观察到显著信号。相应的90%置信水平乘积分支比上限被设定为：对于$\eta_{c}(1S)$跃迁为$5.0 \times 10^{-6}$，对于$\eta_{c}(2S)$跃迁为$3.7 \times 10^{-6}$。部分衰变宽度的90%置信水平上限也被报告为$\Gamma(\psi(3770) \to \gamma \eta_{c}(1S)) < 5.5$ keV和$\Gamma(\psi(3770) \to \gamma \eta_{c}(2S)) < 29.4$ keV。与之前使用的积分亮度相比，本次使用的积分亮度约为其七倍，这些结果分别将$\eta_{c}(1S)$和$\eta_{c}(2S)$跃迁的上限降低了约三倍和两倍。
英文摘要：
Based on an integrated luminosity of $20.3~\mathrm{fb}^{-1}$ of $e^{+}e^{-}$ annihilation data collected at a center-of-mass energy of $3.773~\rm{GeV}$ with the BESIII detector operating at the BEPCII collider, an improved search for the radiative transitions $ψ(3770) \to γη_{c}(1S, 2S)$ is performed using the hadronic decays $η_{c}(1S, 2S) \to K^{0}_{S} K^{\pm} π^{\mp}$. No significant signal is observed. The corresponding 90$\%$ confidence level upper limits on the product branching fractions are set to be $5.0 \times 10^{-6}$ for the $η_{c}(1S)$ transition and $3.7 \times 10^{-6}$ for the $η_{c}(2S)$ transition. The 90$\%$ confidence level upper limits on the partial decay widths are also reported to be $Γ(ψ(3770) \to γη_{c}(1S)) < 5.5$ keV and $Γ(ψ(3770) \to γη_{c}(2S)) < 29.4~\rm{keV}$. With about seven times larger integrated luminosity than used previously, these results lower the upper limits by approximately a factor of three and two for the $η_{c}(1S)$ and $η_{c}(2S)$ transitions, respectively.
