The MicroBooNE liquid argon time projection chamber (LArTPC) maintains a high level of liquid argon purity through the use of a filtration system that removes electronegative contaminants in ...continuously-circulated liquid, recondensed boil off, and externally supplied argon gas. We use the MicroBooNE LArTPC to reconstruct MeV-scale radiological decays. Using this technique we measure the liquid argon filtration system's efficacy at removing radon. This is studied by placing a 500 kBq \(^{222}\)Rn source upstream of the filters and searching for a time-dependent increase in the number of radiological decays in the LArTPC. In the context of two models for radon mitigation via a liquid argon filtration system, a slowing mechanism and a trapping mechanism, MicroBooNE data supports a radon reduction factor of greater than 99.999% or 97%, respectively. Furthermore, a radiological survey of the filters found that the copper-based filter material was the primary medium that removed the \(^{222}\)Rn. This is the first observation of radon mitigation in liquid argon with a large-scale copper-based filter and could offer a radon mitigation solution for future large LArTPCs.
In this letter we present the first measurements of an exclusive electron
neutrino cross section with the MicroBooNE experiment using data from the
Booster Neutrino Beamline at Fermilab. These ...measurements are made for a
selection of charged-current electron neutrinos without final-state pions.
Differential cross sections are extracted in energy and angle with respect to
the beam for the electron and the leading proton. The differential cross
section as a function of proton energy is measured using events with protons
both above and below the visibility threshold. This is done by including a
separate selection of electron neutrino events without reconstructed proton
candidates in addition to those with proton candidates. Results are compared to
the predictions from several modern generators, and we find the data agrees
well with these models. The data shows best agreement, as quantified by
$p$-value, with the generators that predict a lower overall cross section, such
as GENIE v3 and NuWro.
Primary challenges for current and future precision neutrino experiments using liquid argon time projection chambers (LArTPCs) include understanding detector effects and quantifying the associated ...systematic uncertainties. This paper presents a novel technique for assessing and propagating LArTPC detector-related systematic uncertainties. The technique makes modifications to simulation waveforms based on a parameterization of observed differences in ionization signals from the TPC between data and simulation, while remaining insensitive to the details of the detector model. The modifications are then used to quantify the systematic differences in low- and high-level reconstructed quantities. This approach could be applied to future LArTPC detectors, such as those used in SBN and DUNE.
In this article, we describe a modified implementation of Mask Region-based Convolutional Neural Networks (Mask-RCNN) for cosmic ray muon clustering in a liquid argon TPC and applied to MicroBooNE ...neutrino data. Our implementation of this network, called sMask-RCNN, uses sparse submanifold convolutions to increase processing speed on sparse datasets, and is compared to the original dense version in several metrics. The networks are trained to use wire readout images from the MicroBooNE liquid argon time projection chamber as input and produce individually labeled particle interactions within the image. These outputs are identified as either cosmic ray muon or electron neutrino interactions. We find that sMask-RCNN has an average pixel clustering efficiency of 85.9% compared to the dense network's average pixel clustering efficiency of 89.1%. We demonstrate the ability of sMask-RCNN used in conjunction with MicroBooNE's state-of-the-art Wire-Cell cosmic tagger to veto events containing only cosmic ray muons. The addition of sMask-RCNN to the Wire-Cell cosmic tagger removes 70% of the remaining cosmic ray muon background events at the same electron neutrino event signal efficiency. This event veto can provide 99.7% rejection of cosmic ray-only background events while maintaining an electron neutrino event-level signal efficiency of 80.1%. In addition to cosmic ray muon identification, sMask-RCNN could be used to extract features and identify different particle interaction types in other 3D-tracking detectors.
We report the first measurement of $\pi^0$ production in neutral current (NC)
interactions on argon with average neutrino energy of $\lesssim1$~GeV. We use
data from the MicroBooNE detector's ...85-tonne active volume liquid argon time
projection chamber situated in Fermilab's Booster Neutrino Beam and exposed to
$5.89\times10^{20}$ protons on target for this measurement. Measurements of NC
$\pi^0$ events are reported for two exclusive event topologies without charged
pions. Those include a topology with two photons from the decay of the $\pi^0$
and one proton and a topology with two photons and zero protons. Flux-averaged
cross-sections for each exclusive topology and for their semi-inclusive
combination are extracted (efficiency-correcting for two-plus proton final
states), and the results are compared to predictions from the \textsc{genie},
\textsc{neut}, and \textsc{NuWro} neutrino event generators. We measure cross
sections of $1.243\pm0.185$ (syst) $\pm0.076$ (stat), $0.444\pm0.098\pm0.047$,
and $0.624\pm0.131\pm0.075$ $10^{-38}\textrm{cm}^2/\textrm{Ar}$ for the
semi-inclusive NC$\pi^0$, exclusive NC$\pi^0$+1p, and exclusive NC$\pi^0$+0p
processes, respectively.
A novel tune has been made for the MicroBooNE experiment. The fit uses 4 new parameters within the GENIE v3.0.6 Monte Carlo program. Charged current pionless data from the T2K experiment was used. ...New uncertainties were obtained. These results will be used in future MicroBooNE analyses.
We present a measurement of electron neutrino interactions from the Fermilab Booster Neutrino Beam using the MicroBooNE liquid argon time projection chamber to address the nature of the excess of low ...energy interactions observed by the MiniBooNE collaboration. Three independent electron neutrino searches are performed across multiple single electron final states, including an exclusive search for two-body scattering events with a single proton, a semi-inclusive search for pion-less events, and a fully inclusive search for events containing all hadronic final states. With differing signal topologies, statistics, backgrounds, reconstruction algorithms, and analysis approaches, the results are found to be consistent with the nominal electron neutrino rate expectations from the Booster Neutrino Beam and no excess of electron neutrino events is observed.
We report a measurement of the energy-dependent total charged-current cross section \(\sigma\left(E_\nu\right)\) for inclusive muon neutrinos scattering on argon, as well as measurements of ...flux-averaged differential cross sections as a function of muon energy and hadronic energy transfer (\(\nu\)). Data corresponding to 5.3\(\times\)10\(^{19}\) protons on target of exposure were collected using the MicroBooNE liquid argon time projection chamber located in the Fermilab Booster Neutrino Beam with a mean neutrino energy of approximately 0.8 GeV. The mapping between the true neutrino energy \(E_\nu\) and reconstructed neutrino energy \(E^{rec}_\nu\) and between the energy transfer \(\nu\) and reconstructed hadronic energy \(E^{rec}_{had}\) are validated by comparing the data and Monte Carlo (MC) predictions. In particular, the modeling of the missing hadronic energy and its associated uncertainties are verified by a new method that compares the \(E^{rec}_{had}\) distributions between data and an MC prediction after constraining the reconstructed muon kinematic distributions, energy and polar angle, to those of data. The success of this validation gives confidence that the missing energy in the MicroBooNE detector is well-modeled and underpins first-time measurements of both the total cross section \(\sigma\left(E_\nu\right)\) and the differential cross section \(d\sigma/d\nu\) on argon.
In this white paper, we outline some of the scientific opportunities and challenges related to detection and reconstruction of low-energy (less than 100 MeV) signatures in liquid argon ...time-projection chamber (LArTPC) detectors. Key takeaways are summarized as follows. 1) LArTPCs have unique sensitivity to a range of physics and astrophysics signatures via detection of event features at and below the few tens of MeV range. 2) Low-energy signatures are an integral part of GeV-scale accelerator neutrino interaction final states, and their reconstruction can enhance the oscillation physics sensitivities of LArTPC experiments. 3) BSM signals from accelerator and natural sources also generate diverse signatures in the low-energy range, and reconstruction of these signatures can increase the breadth of BSM scenarios accessible in LArTPC-based searches. 4) Neutrino interaction cross sections and other nuclear physics processes in argon relevant to sub-hundred-MeV LArTPC signatures are poorly understood. Improved theory and experimental measurements are needed. Pion decay-at-rest sources and charged particle and neutron test beams are ideal facilities for experimentally improving this understanding. 5) There are specific calibration needs in the low-energy range, as well as specific needs for control and understanding of radiological and cosmogenic backgrounds. 6) Novel ideas for future LArTPC technology that enhance low-energy capabilities should be explored. These include novel charge enhancement and readout systems, enhanced photon detection, low radioactivity argon, and xenon doping. 7) Low-energy signatures, whether steady-state or part of a supernova burst or larger GeV-scale event topology, have specific triggering, DAQ and reconstruction requirements that must be addressed outside the scope of conventional GeV-scale data collection and analysis pathways.
We present the first measurement of the single-differential \(\nu_e + \bar{\nu}_e\) charged-current inclusive cross sections on argon in electron or positron energy and in electron or positron ...scattering cosine over the full angular range. Data were collected using the MicroBooNE liquid argon time projection chamber located off-axis from the Fermilab Neutrinos at the Main Injector beam over an exposure of \(2.0\times10^{20}\) protons on target. The signal definition includes a 60 MeV threshold on the \(\nu_e\) or \(\bar{\nu}_e\) energy and a 120 MeV threshold on the electron or positron energy. The measured total and differential cross sections are found to be in agreement with the GENIE, NuWro, and GiBUU neutrino generators.
