Reconstructing neutrinoless double beta decay event kinematics in a xenon gas detector with vertex tagging

TL;DR

This paper investigates how well a future xenon gas detector can measure key kinematic variables of neutrinoless double beta decay events, crucial for understanding the underlying physics, with a focus on vertex tagging and detector resolution.

Contribution

It demonstrates the potential to accurately reconstruct decay kinematics in a xenon gas detector with vertex tagging, informing future experimental designs.

Findings

Reconstruction of cosθ with 0.19 precision

Electron energy T1 reconstructed with 110 keV precision

Feasibility shown with 10 detected decay events

Abstract

If neutrinoless double beta decay is discovered, the next natural step would be understanding the lepton number violating physics responsible for it. Several alternatives exist beyond the exchange of light neutrinos. Some of these mechanisms can be distinguished by measuring phase-space observables, namely the opening angle $\cos\theta$ among the two decay electrons, and the electron energy spectra, $T_1$ and $T_2$. In this work, we study the statistical accuracy and precision in measuring these kinematic observables in a future xenon gas detector with the added capability to precisely locate the decay vertex. For realistic detector conditions (a gas pressure of 10 bar and spatial resolution of 4 mm), we find that the average $\overline{\cos\theta}$ and $\overline{T_1}$ values can be reconstructed with a precision of 0.19 and 110 keV, respectively, assuming that only 10 neutrinoless double beta decay events are detected.