The Aerogel Ring Imaging Cherenkov (ARICH) counter serves as a particle identification device in the forward end-cap region of the Belle II spectrometer. It is capable of identifying pions and kaons with momenta up to $4 \, {\rm GeV}/c$ by detecting Cherenkov photons emitted in the silica aerogel radiator. After the detector alignment and calibration of the probability density function, we evaluate the performance of the ARICH counter using early beam collision data. Event samples of $D^{\ast +} \to D^0 \pi^+ (D^0 \to K^-\pi^+)$ were used to determine the $\pi(K)$ efficiency and the $K(\pi)$ misidentification probability. We found that the ARICH counter is capable of separating kaons from pions with an identification efficiency of $93.5 \pm 0.6 \, \%$ at a pion misidentification probability of $10.9 \pm 0.9 \, \%$. This paper describes the identification method of the counter and the evaluation of the performance during its early operation.

中文翻译：

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使用早期光束碰撞数据评估 Belle II 光谱仪的气凝胶 RICH 计数器的性能

气凝胶环成像 Cherenkov (ARICH) 计数器用作 Belle II 光谱仪前端盖区域中的粒子识别设备。通过检测二氧化硅气凝胶散热器中发射的切伦科夫光子，它能够识别动量高达 $4 \, {\rm GeV}/c$ 的介子和介子。在探测器对准和概率密度函数校准后，我们​​使用早期光束碰撞数据评估 ARICH 计数器的性能。$D^{\ast +} \to D^0 \pi^+ (D^0 \to K^-\pi^+)$ 的事件样本用于确定 $\pi(K)$ 效率和$K(\pi)$ 误识别概率。我们发现 ARICH 计数器能够以 $93.5 \pm 0.6 \, \%$ 的识别效率将 kaons 与 pion 分开，而 pion 错误识别概率为 $10.9 \pm 0.9 \, \%$。