0νββ discrimination of single-crystal multielectrode readout of high purity germanium detector ⁷⁶Ge

Abstract

<p indent="0mm">Experiments conducted to investigate the neutrinoless double-beta (0νββ) decay of ⁷⁶Ge using a high purity germanium (HPGe) detector heavily rely on background suppression technologies to enhance their sensitivities. Differentiating between single-electron (background) and double-electron (0νββ) events is challenging because of the minimal discrimination between their respective signal characteristics. In this article, a waveform-simulation method is established for a single-crystal multielectrode HPGe detector, and the position resolution of the double-sided crossed-strip multielectrode HPGe detector is investigated. At the same time, the lightGBM model is built to classify and train the simulated waveforms collected by each electrode of the multielectrode HPGe detector. The results reveal that the multielectrode HPGe detector demonstrates good position sensitivity in the direction of electrode distribution. The depth of particle interaction can be determined by the time difference between waveforms collected by the electrodes. Based on the lightGBM model, the recognition effect of the 0νββ double-electron events is 68.4%. The trained lightGBM model has been verified to exhibit a remarkable inhibitory effect on ⁶⁸Ge and ⁶⁰Co in the background. This can be attributed to the fact that the 0νββ signal event is not substantially inhibited and can therefore be inhibited by 3.33 and 2.66 times before and after the discrimination, respectively. The results show that the multielectrode HPGe detector can be feasibly applied to the 0νββ decay detection of ⁷⁶Ge, which provides a reference for future event-by-event research on the 0νββ decay of ⁷⁶Ge in the China Jinping Underground Laboratory.</p>

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