Development of a simulation and analysis framework for N{\nu}DEx experiment

TL;DR

This paper introduces a comprehensive simulation and analysis framework for the NνDEx experiment, enabling detailed detector design, event reconstruction, and background discrimination for neutrinoless double beta decay searches in $^{82}$Se.

Contribution

The paper develops a specialized simulation and analysis framework combining ion mobility calculations, electric field modeling, event generation, and machine learning-based event classification for NνDEx.

Findings

Ion mobility values with 3% uncertainty were obtained.

Electric field and charge transport were accurately modeled in the detector geometry.

Boosted decision trees effectively separate signal from background.

Abstract

N$\nu$DEx aims to search for the neutrinoless double beta decay in $^{82}$Se using a high pressure $^{82}$SeF$_6$ gas time projection chamber (TPC). This paper presents a simulation and analysis framework developed specifically for the N$\nu$DEx experiment. Using density functional theory and two-temperature theory, the reduced mobilities of SeF$_5^-$ and SeF$_6^-$ ions in SeF$_6$ were calculated, yielding values of 0.444 and 0.430 $\mathrm{cm^2V^{-1}s^{-1}}$ respectively, with an estimated uncertainty within 3\%. The TPC geometry, featuring a cathode, focusing plane, and anode structure, was modeled in COMSOL to compute electric fields. Signal and background events were generated using BxDecay0 and Geant4, while Garfield++ was employed to simulate charge transport and signal induction. Three-dimensional tracks were reconstructed from drift-time differences between the two assumed ion species using a breadth-first search algorithm. To demonstrate the framework's analytical capability, topological variables were taken from reconstructed tracks and used to define selection criteria. A boosted decision tree was then implemented to benchmark the signal-background separation. This simulation framework successfully validates the complete experimental workflow, serving as a robust tool for detector design and future sensitivity studies in the N$\nu$DEx experiment.