[Paper Review] Neutrino Event Selection in the MicroBooNE Liquid Argon Time Projection Chamber using Wire-Cell 3-D Imaging, Clustering, and Charge-Light Matching

P. Abratenko|arXiv (Cornell University)|Nov 2, 2020

Neutrino Physics Research27 references32 citations

TL;DR

This paper presents a novel 3D event reconstruction framework for the MicroBooNE liquid argon time projection chamber (LArTPC), leveraging Wire-Cell 3D imaging, adaptive clustering, and many-to-many charge-light matching to achieve high-efficiency neutrino event selection. The method reduces non-beam-coincident cosmic-ray muons by a factor of 30 while achieving 95% efficiency in selecting neutrino charged-current interactions with over 80% of selected events reconstructed at ≥70% completeness and ≥80% purity.

ABSTRACT

Abstract An accurate and efficient event reconstruction is required to realize the full scientific capability of liquid argon time projection chambers (LArTPCs). The current and future neutrino experiments that rely on massive LArTPCs create a need for new ideas and reconstruction approaches. Wire-Cell, proposed in recent years, is a novel tomographic event reconstruction method for LArTPCs. The Wire-Cell 3D imaging approach capitalizes on charge, sparsity, time, and geometry information to reconstruct a topology-agnostic 3D image of the ionization electrons prior to pattern recognition. A second novel method, the many-to-many charge-light matching, then pairs the TPC charge activity to the detected scintillation light signal, thus enabling a powerful rejection of cosmic-ray muons in the MicroBooNE detector. A robust processing of the scintillation light signal and an appropriate clustering of the reconstructed 3D image are fundamental to this technique. In this paper, we describe the principles and algorithms of these techniques and their successful application in the MicroBooNE experiment. A quantitative evaluation of the performance of these techniques is presented. Using these techniques, a 95% efficient pre-selection of neutrino charged-current events is achieved with a 30-fold reduction of non-beam-coincident cosmic-ray muons, and about 80% of the selected neutrino charged-current events are reconstructed with at least 70% completeness and 80% purity.

Motivation & Objective

• Address the challenge of reconstructing neutrino interactions in large-scale LArTPCs amid high cosmic-ray backgrounds and detector imperfections.
• Develop a topology-agnostic 3D imaging method that reconstructs ionization electron topology before pattern recognition.
• Enable robust charge-light matching to distinguish beam-induced neutrino events from cosmic-ray muons.
• Improve reconstruction accuracy and efficiency in the presence of nonfunctional wires, signal processing gaps, and detector noise.
• Achieve high completeness and purity in reconstructed neutrino interactions for downstream physics analysis.

Proposed method

• Wire-Cell 3D imaging reconstructs ionization electron topology using charge, time, geometry, and sparsity constraints, avoiding early pattern recognition.
• Tiling is applied to handle wire readout ambiguities and improve spatial resolution, especially for isochronous and prolonged tracks.
• Charge solving uses a tomographic approach to reconstruct 3D charge distributions from 2D wire signals, minimizing degeneracies from integrated charge measurements.
• De-ghosting removes spurious charge structures by enforcing positivity and proximity constraints on reconstructed clusters.
• 3D clustering groups ionization signals into physically meaningful clusters based on spatial and temporal proximity.
• Many-to-many charge-light matching pairs TPC clusters with scintillation light flashes from PMTs, enabling effective cosmic-ray muon rejection.

Experimental results

Research questions

• RQ1 Can Wire-Cell 3D imaging achieve high-fidelity reconstruction of ionization electron topology in LArTPCs without prior pattern recognition?
• RQ2 How effectively can charge-light matching using 3D clustering suppress non-beam-coincident cosmic-ray muons in the MicroBooNE detector?
• RQ3 To what extent do nonfunctional wires and signal processing gaps degrade reconstruction performance, and can they be mitigated?
• RQ4 How does the performance of 3D imaging and charge-light matching vary under realistic conditions including neutrino-only and neutrino-plus-cosmic scenarios?
• RQ5 What level of completeness and purity can be achieved in reconstructed neutrino interactions using this framework?

Key findings

• A 95% efficient pre-selection of neutrino charged-current interactions is achieved, with a 30-fold reduction in non-beam-coincident cosmic-ray muons.
• Over 80% of selected neutrino charged-current events are reconstructed with at least 70% completeness and 80% purity.
• The method reduces unusable detector regions due to nonfunctional wires by a factor of ten through spatial interpolation using functional neighbors.
• In realistic simulations, completeness and purity remain high even with detector defects, signal processing inefficiencies, and overlapping cosmic-ray backgrounds.
• The 3D imaging and charge-light matching pipeline enables high-fidelity reconstruction of neutrino interactions, significantly improving downstream analysis efficiency.
• The framework demonstrates robustness to common LArTPC challenges such as isochronous tracks and signal gaps, with trajectory fitting expected to further improve resolution.