Demonstration of Event Position Reconstruction based on Diffusion in the NEXT-White Detector

TL;DR

This paper demonstrates a novel method for reconstructing event positions in a xenon gas time projection chamber by analyzing electron diffusion, achieving high accuracy without relying on primary scintillation signals.

Contribution

It introduces diffusion-based position reconstruction techniques using neural networks and calibration data, offering an alternative to traditional scintillation-based methods in noble element detectors.

Findings

Achieved 2 cm position accuracy for low-energy events using $^{83m}$Kr calibration.

Used neural networks to determine event barycenter with 3 cm precision for high-energy tracks.

Indicated potential for sub-1% energy calibration and fiducialization in large detectors.

Abstract

Noble element time projection chambers are a leading technology for rare event detection in physics, such as for dark matter and neutrinoless double beta decay searches. Time projection chambers typically assign event position in the drift direction using the relative timing of prompt scintillation and delayed charge collection signals, allowing for reconstruction of an absolute position in the drift direction. In this paper, alternate methods for assigning event drift distance via quantification of electron diffusion in a pure high pressure xenon gas time projection chamber are explored. Data from the NEXT-White detector demonstrate the ability to achieve good position assignment accuracy for both high- and low-energy events. Using point-like energy deposits from $^{83\mathrm{m}}$Kr calibration electron captures ($E\sim45$keV), the position of origin of low-energy events is determined to $2~$cm precision with bias $< 1$mm. A convolutional neural network approach is then used to quantify diffusion for longer tracks (E$\geq$1.5MeV), yielding a precision of 3cm on the event barycenter. The precision achieved with these methods indicates the feasibility energy calibrations of better than 1% FWHM at Q$_{\beta\beta}$ in pure xenon, as well as the potential for event fiducialization in large future detectors using an alternate method that does not rely on primary scintillation.