We report on the first measurement of flux-integrated single differential cross sections for charged-current (CC) muon neutrino (νμ) scattering on argon with a muon and a proton in the final state, ...Ar40 (νμ,μp)X. The measurement was carried out using the Booster Neutrino Beam at Fermi National Accelerator Laboratory and the MicroBooNE liquid argon time projection chamber detector with an exposure of 4.59×1019 protons on target. Events are selected to enhance the contribution of CC quasielastic (CCQE) interactions. The data are reported in terms of a total cross section as well as single differential cross sections in final state muon and proton kinematics. We measure the integrated per-nucleus CCQE-like cross section (i.e., for interactions leading to a muon, one proton, and no pions above detection threshold) of (4.93±0.76stat±1.29sys)×10−38 cm2, in good agreement with theoretical calculations. The single differential cross sections are also in overall good agreement with theoretical predictions, except at very forward muon scattering angles that correspond to low-momentum-transfer events.
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We present an analysis of MicroBooNE data with a signature of one muon, no pions, and at least one proton above a momentum threshold of 300 MeV/c(CC0πNp). This is the first differential cross-section ...measurement of this topology in neutrino-argon interactions. We achieve a significantly lower proton momentum threshold than previous carbon and scintillator-based experiments. Using data collected from a total of approximately 1.6 × 1020 protons on target, we measure the muon neutrino cross section for the CC0πNp interaction channel in argon at MicroBooNE in the Booster Neutrino Beam which has a mean energy of around 800 MeV. We present the results from a data sample with estimated efficiency of 29% and purity of 76% as differential cross sections in five reconstructed variables: the muon momentum and polar angle, the leading proton momentum and polar angle, and the muon-proton opening angle. We include smearing matrices that can be used to "forward fold" theoretical predictions for comparison with these data. We compare the measured differential cross sections to a number of recent theory predictions demonstrating largely good agreement with this first-ever dataset on argon.
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A detailed understanding of inclusive muon neutrino charged-current interactions on argon is crucial to the study of neutrino oscillations in current and future experiments using liquid argon time ...projection chambers. To that end, we report a comprehensive set of differential cross section measurements for this channel that simultaneously probe the leptonic and hadronic systems by dividing the channel into final states with and without protons. Measurements of the proton kinematics and proton multiplicity of the final state are also presented. For these measurements, we utilize data collected with the MicroBooNE detector from 6.4 × 10 20 protons on target from the Fermilab booster neutrino beam at a mean neutrino energy of approximately 0.8 GeV. We present in detail the cross section extraction procedure, including the unfolding, and model validation that uses data to model comparisons and the conditional constraint formalism to detect mismodeling that may introduce biases to extracted cross sections that are larger than their uncertainties. The validation exposes insufficiencies in the overall model, motivating the inclusion of an additional data-driven reweighting systematic to ensure the accuracy of the unfolding. The extracted results are compared to a number of event generators and their performance is discussed with a focus on the regions of phase space that indicate the greatest need for modeling improvements. Published by the American Physical Society 2024
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We present the first measurement of the cross section of Cabibbo-suppressed Λ baryon production, using data collected with the MicroBooNE detector when exposed to the neutrinos from the main injector ...beam at the Fermi National Accelerator Laboratory. The data analyzed correspond to 2.2×1020 protons on target running in neutrino mode, and 4.9×1020 protons on target running in anti-neutrino mode. An automated selection is combined with hand scanning, with the former identifying five candidate Λ production events when the signal was unblinded, consistent with the GENIE prediction of 5.3±1.1 events. Several scanners were employed, selecting between three and five events, compared with a prediction from a blinded Monte Carlo simulation study of 3.7±1.0 events. Restricting the phase space to only include Λ baryons that decay above MicroBooNE’s detection thresholds, we obtain a flux averaged cross section of 2.0-1.7+2.2×10-40 cm2/Ar , where statistical and systematic uncertainties are combined.
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Abstract We present a novel methodology to search for intranuclear neutron-antineutron transition (n⟶ n̅ ) followed by n̅ -nucleon annihilation within an 40 Ar nucleus, using the MicroBooNE liquid ...argon time projection chamber (LArTPC) detector. A discovery of n⟶ n̅ transition or a new best limit on the lifetime of this process would either constitute physics beyond the Standard Model or greatly constrain theories of baryogenesis, respectively. The approach presented in this paper makes use of deep learning methods to select n⟶ n̅ events based on their unique features and differentiate them from cosmogenic backgrounds. The achieved signal and background efficiencies are (70.22 ± 6.04)% and (0.0020 ± 0.0003)%, respectively. A demonstration of a search is performed with a data set corresponding to an exposure of 3.32 ×10 26 neutron-years, and where the background rate is constrained through direct measurement, assuming the presence of a negligible signal. With this approach, no excess of events over the background prediction is observed, setting a demonstrative lower bound on the n⟶ n̅ lifetime in 40 Ar of τ m ≳ 1.1×10 26 years, and on the free n⟶ n̅ transition time of τ n⟶ n̅ ≳ 2.6×10 5 s, each at the 90% confidence level. This analysis represents a first-ever proof-of-principle demonstration of the ability to search for this rare process in LArTPCs with high efficiency and low background.
We report 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 222Rn 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 97% or 99.999%, respectively. Furthermore, a radiological survey of the filters found that the copper-based filter material was the primary medium that removed the 222Rn. 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.
We present a novel methodology to search for intranuclearneutron-antineutron transition (n⟶n̅) followed by n̅-nucleon annihilation within an 40Ar nucleus, usingthe MicroBooNE liquid argon time ...projection chamber (LArTPC)detector. A discovery of n⟶n̅ transition or a newbest limit on the lifetime of this process would either constitutephysics beyond the Standard Model or greatly constrain theories ofbaryogenesis, respectively. The approach presented in this papermakes use of deep learning methods to select n⟶n̅ events based on their unique features and differentiate them fromcosmogenic backgrounds. The achieved signal and backgroundefficiencies are (70.22 ± 6.04)% and (0.0020 ± 0.0003)%,respectively. A demonstration of a search is performed with a dataset corresponding to an exposure of3.32 ×1026 neutron-years, and where the background rateis constrained through direct measurement, assuming the presence ofa negligible signal. With this approach, no excess of events overthe background prediction is observed, setting a demonstrative lowerbound on the n⟶n̅ lifetime in 40Ar ofτm ≳ 1.1×1026 years, and on the freen⟶n̅ transition time ofτn⟶n̅ ≳ 2.6×105 s,each at the 90% confidence level. This analysis represents afirst-ever proof-of-principle demonstration of the ability to searchfor this rare process in LArTPCs with high efficiency and lowbackground.
Abstract
This article presents the reconstruction of the
electromagnetic activity from electrons and photons (showers) used
in the MicroBooNE deep learning-based low energy electron
search. The ...reconstruction algorithm uses a combination of
traditional and deep learning-based techniques to estimate shower
energies. We validate these predictions using two
ν
μ
-sourced data samples: charged/neutral current
interactions with final state neutral pions and charged current
interactions in which the muon stops and decays within the detector
producing a Michel electron. Both the neutral pion sample and
Michel electron sample demonstrate agreement between data and
simulation. Further, the absolute shower energy scale is shown to be
consistent with the relevant physical constant of each sample: the
neutral pion mass peak and the Michel energy cutoff.
Accurate knowledge of electron transport properties is vital to understanding the information provided by liquid argon time projection chambers (LArTPCs). Ionization electron drift-lifetime, local ...electric field distortions caused by positive ion accumulation, and electron diffusion can all significantly impact the measured signal waveforms. This paper presents a measurement of the effective longitudinal electron diffusion coefficient, DL, in MicroBooNE at the nominal electric field strength of 273.9 V/cm. Historically, this measurement has been made in LArTPC prototype detectors. This represents the first measurement in a large-scale (85 tonne active volume) LArTPC operating in a neutrino beam. This is the largest dataset ever used for this measurement. Using a sample of ~70,000 through-going cosmic ray muon tracks tagged with MicroBooNE's cosmic ray tagger system, we measure DL = 3.74+0.28-0.29 cm2/s.
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