SBND is the near detector of the Short-Baseline Neutrino program at Fermilab. Its location near to the Booster Neutrino Beam source and relatively large mass will allow the study of neutrino ...interactions on argon with unprecedented statistics. This paper describes the expected performance of the SBND photon detection system, using a simulated sample of beam neutrinos and cosmogenic particles. Its design is a dual readout concept combining a system of 120 photomultiplier tubes, used for triggering, with a system of 192 X-ARAPUCA devices, located behind the anode wire planes. Furthermore, covering the cathode plane with highly-reflective panels coated with a wavelength-shifting compound recovers part of the light emitted towards the cathode, where no optical detectors exist. We show how this new design provides a high light yield and a more uniform detection efficiency, an excellent timing resolution and an independent 3D-position reconstruction using only the scintillation light. Finally, the whole reconstruction chain is applied to recover the temporal structure of the beam spill, which is resolved with a resolution on the order of nanoseconds.
We present a first search for dark-trident scattering in a neutrino beam using a data set corresponding to \(7.2 \times 10^{20}\) protons on target taken with the MicroBooNE detector at Fermilab. ...Proton interactions in the neutrino target at the Main Injector produce \(\pi^0\) and \(\eta\) mesons, which could decay into dark-matter (DM) particles mediated via a dark photon \(A^\prime\). A convolutional neural network is trained to identify interactions of the DM particles in the liquid-argon time projection chamber (LArTPC) exploiting its image-like reconstruction capability. In the absence of a DM signal, we provide limits at the \(90\%\) confidence level on the squared kinematic mixing parameter \(\varepsilon^2\) as a function of the dark-photon mass in the range \(10\le M_{A^\prime}\le 400\) MeV. The limits cover previously unconstrained parameter space for the production of fermion or scalar DM particles \(\chi\) for two benchmark models with mass ratios \(M_{\chi}/M_{A^\prime}=0.6\) and \(2\) and for dark fine-structure constants \(0.1\le\alpha_D\le 1\).
We present a set of new generalized kinematic imbalance variables that can be measured in neutrino scattering. These variables extend previous measurements of kinematic imbalance on the transverse ...plane, and are more sensitive to modeling of nuclear effects. We demonstrate the enhanced power of these variables using simulation, and then use the MicroBooNE detector to measure them for the first time. We report flux-integrated single- and double-differential measurements of charged-current muon neutrino scattering on argon using a topolgy with one muon and one proton in the final state as a function of these novel kinematic imbalance variables. These measurements allow us to demonstrate that the treatment of charged current quasielastic interactions in GENIE version 2 is inadequate to describe data. Further, they reveal tensions with more modern generator predictions particularly in regions of phase space where final state interactions are important.
We present a measurement of neutral pion production in charged-current interactions using data recorded with the MicroBooNE detector exposed to Fermilab's booster neutrino beam. The signal comprises ...one muon, one neutral pion, any number of nucleons, and no charged pions. Studying neutral pion production in the MicroBooNE detector provides an opportunity to better understand neutrino-argon interactions, and is crucial for future accelerator-based neutrino oscillation experiments. Using a dataset corresponding to \(6.86 \times 10^{20}\) protons on target, we present single-differential cross sections in muon and neutral pion momenta, scattering angles with respect to the beam for the outgoing muon and neutral pion, as well as the opening angle between the muon and neutral pion. Data extracted cross sections are compared to generator predictions. We report good agreement between the data and the models for scattering angles, except for an over-prediction by generators at muon forward angles. Similarly, the agreement between data and the models as a function of momentum is good, except for an underprediction by generators in the medium momentum ranges, \(200-400\) MeV for muons and \(100-200\) MeV for pions.
We report the first double-differential cross section measurement of
neutral-current neutral pion (NC$\pi^0$) production in neutrino-argon
scattering, as well as single-differential measurements of ...the same channel in
terms of final states with and without protons. The kinematic variables of
interest for these measurements are the $\pi^0$ momentum and the $\pi^0$
scattering angle with respect to the neutrino beam. A total of 4971 candidate
NC$\pi^0$ events fully-contained within the MicroBooNE detector are selected
using data collected at a mean neutrino energy of $\sim 0.8$ GeV from
$6.4\times10^{20}$ protons on target from the Booster Neutrino Beam at the
Fermi National Accelerator Laboratory. After extensive data-driven model
validation to ensure unbiased unfolding, the Wiener-SVD method is used to
extract nominal flux-averaged cross sections. The results are compared to
predictions from commonly used neutrino event generators, which tend to
overpredict the measured NC$\pi^0$ cross section, especially in the 0.2-0.5
GeV/c $\pi^0$ momentum range, at forward scattering angles, and when at least
one proton is present in the final state. These measurements show sensitivity
to a variety of features that complicate the description of NC$\pi^0$
production including the form factors describing the elementary neutrino
interaction and the final state interactions of the outgoing particles in the
residual argon nucleus. This data will help improve the modeling of NC$\pi^0$
production, which represents a major background in measurements of
charge-parity violation in the neutrino sector and in searches for new physics
beyond the Standard Model.
Charged-current neutrino interactions with final states containing zero mesons and at least one proton are of high interest for current and future accelerator-based neutrino oscillation experiments. ...Using the Booster Neutrino Beam and the MicroBooNE detector at Fermi National Accelerator Laboratory, we have obtained the first double-differential cross section measurements of this channel for muon neutrino scattering on an argon target with a proton momentum threshold of 0.25 GeV/c. We also report a flux-averaged total cross section of \(\sigma = (11.8 \pm 1.2) \times 10^{-38}\) cm\(^2\) / Ar and several single-differential measurements which extend and improve upon previous results. Statistical and systematic uncertainties are quantified with a full treatment of correlations across 359 kinematic bins, including correlations between distributions describing different observables. The resulting data set provides the most detailed information obtained to date for testing models of mesonless neutrino-argon scattering.
We report measurements of radon progeny in liquid argon within the MicroBooNE time projection chamber (LArTPC). The presence of specific radon daughters in MicroBooNE's 85 metric tons of active ...liquid argon bulk is probed with newly developed charge-based low-energy reconstruction tools and analysis techniques to detect correlated \(^{214}\)Bi-\(^{214}\)Po radioactive decays. Special datasets taken during periods of active radon doping enable new demonstrations of the calorimetric capabilities of single-phase neutrino LArTPCs for \(\beta\) and \(\alpha\) particles with electron-equivalent energies ranging from 0.1 to 3.0 MeV. By applying \(^{214}\)Bi-\(^{214}\)Po detection algorithms to data recorded over a 46-day period, no statistically significant presence of radioactive \(^{214}\)Bi is detected, and a limit on the activity is placed at \(<0.35\) mBq/kg at the 95% confidence level. This bulk \(^{214}\)Bi radiopurity limit -- the first ever reported for a liquid argon detector incorporating liquid-phase purification -- is then further discussed in relation to the targeted upper limit of 1 mBq/kg on bulk \(^{222}\)Rn activity for the DUNE neutrino detector.
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$\times10^{20}$ 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.
We report the first double-differential neutrino-argon cross section measurement made simultaneously for final states with and without protons for the inclusive muon neutrino charged-current ...interaction channel. The proton kinematics of this channel are further explored with a differential cross section measurement as a function of the leading proton's kinetic energy that extends across the detection threshold. These measurements utilize data collected using the MicroBooNE detector from 6.4\(\times10^{20}\) protons on target from the Fermilab Booster Neutrino Beam with a mean neutrino energy of \(\sim\)0.8 GeV. Extensive data-driven model validation utilizing the conditional constraint formalism is employed. This motivates enlarging the uncertainties with an empirical reweighting approach to minimize the possibility of extracting biased cross section results. The extracted nominal flux-averaged cross sections are compared to widely used event generator predictions revealing severe mismodeling of final states without protons for muon neutrino charged-current interactions, possibly from insufficient treatment of final state interactions. These measurements provide a wealth of new information useful for improving event generators which will enhance the sensitivity of precision measurements in neutrino experiments.
We present the first search for heavy neutral leptons (HNL) decaying into \(\nu e^+e^-\) or \(\nu\pi^0\) final states in a liquid-argon time projection chamber using data collected with the ...MicroBooNE detector. The data were recorded synchronously with the NuMI neutrino beam from Fermilab's Main Injector corresponding to a total exposure of \(7.01 \times 10^{20}\) protons on target. We set upper limits at the \(90\%\) confidence level on the mixing parameter \(\lvert U_{\mu 4}\rvert^2\) in the mass ranges \(10\le m_{\rm HNL}\le 150\) MeV for the \(\nu e^+e^-\) channel and \(150\le m_{\rm HNL}\le 245\) MeV for the \(\nu\pi^0\) channel, assuming \(\lvert U_{e 4}\rvert^2 = \lvert U_{\tau 4}\rvert^2 = 0\). These limits represent the most stringent constraints in the mass range \(35<m_{\rm HNL}<175\) MeV and the first constraints from a direct search for \(\nu\pi^0\) decays.
