3-D topological signatures and a new discrimination method for single-electron events and 0 νββ events in CdZnTe: A Monte Carlo simulation study

Abstract

In neutrinoless double beta (0νββ) decay experiments, the diversity of topological signatures of different particles provides an important tool to distinguish double beta events from background events and reduce background rates. Aiming at suppressing the single-electron backgrounds which are most challenging, several groups have established Monte Carlo simulation packages to study the topological characteristics of single-electron events and 0νββ events and develop methods to differentiate them. In this paper, applying the knowledge of graph theory, a new topological signature called REF track (Refined Energy-Filtered track) is proposed and proven to be an accurate approximation of the real particle trajectory. Based on the analysis of the energy depositions along the REF track of single-electron events and 0νββ events, the REF energy deposition models for both events are proposed to indicate the significant differences between them. With these differences, this paper presents a new discrimination method, which, in the Monte Carlo simulation, achieved a single-electron rejection factor of 93.8 ± 0.3 (stat.)% as well as a 0νββ efficiency of 85.6 ± 0.4 (stat.)% with optimized parameters in CdZnTe.

Topological background discrimination in the PandaX-III neutrinoless double beta decay experiment

“…Additionally, exploring the use of novel track parameters, or improving the existing ones, can push the conventional background discrimination further. Additional parameters, as the dE/dx along the track, previously studied at [23], and its peculiarities at the end-tracks could allow to improve these results by properly combining them with the parameters studied in this work.…”

“…The different event processes can be combined in sequence to build a more complex processing chain. In REST, only the event data produced in the last event process will be saved to the output file 23 . There are two main reasons why it is not desirable to stock intermediate event data into a single data file 24 .…”

“…The first step of Monte Carlo simulation is to consider PandaX-III as a simple calorimeter and simulate the energy deposition of particles interacting in the gaseous medium, or active 23 However, other metadata information used in the processing chain, e.g. process parameters, simulation conditions, readout definition, or gas properties, will be stored without exception, including previous historical metadata information.…”

A feasibility study of multi-electrode high-purity germanium detector for 76Ge neutrinoless double beta decay searching

“…In 0𝜈𝛽𝛽 experiments, the single-electron background events can be caused by the beta decay of cosmogenic nuclides inside the detector or by the Compton scattering of external gamma. The single-and double-electron signals are quite similar, and the track morphology is complex, so it is challenging to distinguish them [9][10][11]. Therefore, developing single-and double-electron event discrimination methods based on signal characteristics has always been a popular research topic.…”