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

## TL;DR

This paper presents software algorithms for the PandaX-III experiment that significantly reduce background noise in neutrinoless double beta decay detection by analyzing electron track properties, enhancing signal clarity.

## Contribution

Introduces new algorithms within REST software to improve background discrimination using electron track topology and scattering angles in the PandaX-III experiment.

## Key findings

- Background can be reduced by about 7 orders of magnitude.
- Maintains over 20% efficiency for 0νββ detection.
- Demonstrates discrimination of surface background events.

## Abstract

The PandaX-III experiment plans to search for neutrinoless double beta decay (0$\nu\beta\beta$) of $^{136}$Xe in the China JinPing underground Laboratory (CJPL). The experiment will use a high pressure gaseous Time Projection Chamber (TPC) to register both the energy and the electron track topology of an event. This article is devoted to the software side of the experiment. As software tool we use REST, a framework developed for the reconstruction and simulation of TPC-based detector systems. We study the potential for background reduction by introducing appropiate parameters based on the properties of 0$\nu\beta\beta$ events. We exploit for the first time not only the energy density of the electron track-ends, but also the electron scattering angles produced by an electron near the end of its trajectory. To implement this, we have added new algorithms for detector signal and track processing inside REST. Their assessment shows that background can be reduced by about 7 orders of magnitude while keeping 0$\nu\beta\beta$ efficiency above 20% for the PandaX-III baseline readout scheme, a 2-dimensional 3mm-pitch stripped readout. More generally, we use the potential of REST to handle 2D/3D data to assess the impact on signal-to-background significance at different detector granularities, and to validate the PandaX-III baseline choice. Finally, we demonstrate the potential to discriminate surface background events generated at the readout plane in the absence of $t_o$, by making use of event parameters related with the diffusion of electrons.