Phys.Rev. D 105 (2022) 11, 112005 We report a search for an anomalous excess of inclusive charged-current (CC)
$\nu_e$ interactions using the Wire-Cell event reconstruction package in the
MicroBooNE ...experiment, which is motivated by the previous observation of a
low-energy excess (LEE) of electromagnetic events from the MiniBooNE
experiment. With a single liquid argon time projection chamber detector, the
measurements of $\nu_{\mu}$ CC interactions as well as $\pi^0$ interactions are
used to constrain signal and background predictions of $\nu_e$ CC interactions.
A data set collected from February 2016 to July 2018 corresponding to an
exposure of 6.369 $\times$ 10$^{20}$ protons on target from the Booster
Neutrino Beam at FNAL is analyzed. With $x$ representing an overall
normalization factor and referred to as the LEE strength parameter, we select
56 fully contained $\nu_e$ CC candidates while expecting 69.6 $\pm$ 8.0 (stat.)
$\pm$ 5.0 (sys.) and 103.8 $\pm$ 9.0 (stat.) $\pm$ 7.4 (sys.) candidates after
constraints for the absence (eLEE$_{x=0}$) of the median signal strength
derived from the MiniBooNE observation and the presence (eLEE$_{x=1}$) of that
signal strength, respectively. Under a nested hypothesis test using both rate
and shape information in all available channels, the best-fit $x$ is determined
to be 0 (eLEE$_{x=0}$) with a 95.5% confidence level upper limit of $x$ at
0.502. Under a simple-vs-simple hypotheses test, the eLEE$_{x=1}$ hypothesis is
rejected at 3.75$\sigma$, while the eLEE$_{x=0}$ hypothesis is shown to be
consistent with the observation at 0.45$\sigma$. In the context of the eLEE
model, the estimated 68.3% confidence interval of the $\nu_e$ hypothesis to
explain the LEE observed in the MiniBooNE experiment is disfavored at a
significance level of more than 2.6$\sigma$ (3.0$\sigma$) considering
MiniBooNE's full (statistical) uncertainties.
This article presents a measurement of $\nu_e$ interactions without pions in
the final state using the MicroBooNE experiment and an investigation into the
excess of low-energy electromagnetic events ...observed by the MiniBooNE
collaboration. The measurement is performed in exclusive channels with
(1$e$N$p$0$\pi$) and without (1$e$0$p$0$\pi$) visible final-state protons using
6.86$\times 10^{20}$ protons on target of data collected from the Booster
Neutrino Beam at Fermilab. Events are reconstructed with the Pandora pattern
recognition toolkit and selected using additional topological information from
the MicroBooNE liquid argon time projection chamber. Using a goodness-of-fit
test the data are found to be consistent with the predicted number of events
with nominal flux and interaction models with a $p$-value of 0.098 in the two
channels combined. A model based on the low-energy excess observed in MiniBooNE
is introduced to quantify the strength of a possible $\nu_e$ excess. The
analysis suggests that if an excess is present, it is not consistent with a
simple scaling of the $\nu_e$ contribution to the flux. Combined, the
1$e$N$p$0$\pi$ and 1$e$0$p$0$\pi$ channels do not give a conclusive indication
about the tested model, but separately they both disfavor the low-energy excess
model at $>$90% CL. The observation in the most sensitive 1$e$N$p$0$\pi$
channel is below the prediction and consistent with no excess. In the less
sensitive 1$e$0$p$0$\pi$ channel the observation at low energy is above the
prediction, while overall there is agreement over the full energy spectrum.
Phys.Rev.D 105 (2022) 11, 112003 We present a measurement of the $\nu_e$-interaction rate in the MicroBooNE
detector that addresses the observed MiniBooNE anomalous low-energy excess
(LEE). The ...approach taken isolates neutrino interactions consistent with the
kinematics of charged-current quasi-elastic (CCQE) events. The topology of such
signal events has a final state with 1 electron, 1 proton, and 0 mesons
($1e1p$). Multiple novel techniques are employed to identify a $1e1p$ final
state, including particle identification that use two methods of
deep-learning-based image identification, and event isolation using a boosted
decision-tree ensemble trained to recognize two-body scattering kinematics.
This analysis selects 25 $\nu_e$-candidate events in the reconstructed neutrino
energy range of 200--1200\,MeV, while $29.0 \pm 1.9_\text{(sys)} \pm
5.4_\text{(stat)}$ are predicted when using $\nu_\mu$ CCQE interactions as a
constraint. We use a simplified model to translate the MiniBooNE LEE
observation into a prediction for a $\nu_e$ signal in MicroBooNE. A $\Delta
\chi^2$ test statistic, based on the combined Neyman--Pearson $\chi^2$
formalism, is used to define frequentist confidence intervals for the LEE
signal strength. Using this technique, in the case of no LEE signal, we expect
this analysis to exclude a normalization factor of 0.75 (0.98) times the median
MiniBooNE LEE signal strength at 90\% ($2\sigma$) confidence level, while the
MicroBooNE data yield an exclusion of 0.25 (0.38) times the median MiniBooNE
LEE signal strength at 90\% ($2\sigma$) confidence
JINST 16 (2021) 12, T12017 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 $\nu_{\mu}$-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.
Phys.Rev.Lett. 128 (2022) 11, 111801 We report results from a search for neutrino-induced neutral current (NC)
resonant $\Delta$(1232) baryon production followed by $\Delta$ radiative decay,
with a ...$\langle0.8\rangle$~GeV neutrino beam. Data corresponding to
MicroBooNE's first three years of operations (6.80$\times$10$^{20}$ protons on
target) are used to select single-photon events with one or zero protons and
without charged leptons in the final state ($1\gamma1p$ and $1\gamma0p$,
respectively). The background is constrained via an in-situ high-purity
measurement of NC $\pi^0$ events, made possible via dedicated $2\gamma1p$ and
$2\gamma0p$ selections. A total of 16 and 153 events are observed for the
$1\gamma1p$ and $1\gamma0p$ selections, respectively, compared to a constrained
background prediction of $20.5 \pm 3.65 \text{(sys.)} $ and $145.1 \pm 13.8
\text{(sys.)} $ events. The data lead to a bound on an anomalous enhancement of
the normalization of NC $\Delta$ radiative decay of less than $2.3$ times the
predicted nominal rate for this process at the 90% confidence level (CL). The
measurement disfavors a candidate photon interpretation of the MiniBooNE
low-energy excess as a factor of $3.18$ times the nominal NC $\Delta$ radiative
decay rate at the 94.8% CL, in favor of the nominal prediction, and represents
a greater than $50$-fold improvement over the world's best limit on
single-photon production in NC interactions in the sub-GeV neutrino energy
range
In liquid argon time projection chambers exposed to neutrino beams and running on or near surface levels, cosmic muons and other cosmic particles are incident on the detectors while a single ...neutrino-induced event is being recorded. In practice, this means that data from surface liquid argon time projection chambers will be dominated by cosmic particles, both as a source of event triggers and as the majority of the particle count in true neutrino-triggered events. In this work, we demonstrate a novel application of deep learning techniques to remove these background particles by applying semantic segmentation on full detector images from the SBND detector, the near detector in the Fermilab Short-Baseline Neutrino Program. We use this technique to identify, at single image-pixel level, whether recorded activity originated from cosmic particles or neutrino interactions.
Phys. Rev. D 102, 112013 (2020) 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
(CC0$\pi$Np). 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 $1.6 \times
10^{20}$ protons-on-target, we measure the muon neutrino cross section for the
CC0$\pi$Np 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 data set
on argon.
We present a measurement of \(\eta\) production from neutrino interactions on argon with the MicroBooNE detector. The modeling of resonant neutrino interactions on argon is a critical aspect of the ...neutrino oscillation physics program being carried out by the DUNE and Short Baseline Neutrino programs. \(\eta\) production in neutrino interactions provides a powerful new probe of resonant interactions, complementary to pion channels, and is particularly suited to the study of higher-order resonances beyond the \(\Delta(1232)\). We measure a flux-integrated cross section for neutrino-induced \(\eta\) production on argon of \(3.22 \pm 0.84 \; \textrm{(stat.)} \pm 0.86 \; \textrm{(syst.)}\) \(10^{-41}{\textrm{cm}}^{2}\)/nucleon. By demonstrating the successful reconstruction of the two photons resulting from \(\eta\) production, this analysis enables a novel calibration technique for electromagnetic showers in GeV accelerator neutrino experiments.
Phys. Rev. Lett. 125, 201803 (2020) We report on the first measurement of flux-integrated single differential
cross sections for charged-current (CC) muon neutrino ($\nu_\mu$) scattering on
argon ...with a muon and a proton in the final state,
$^{40}$Ar($\nu_\mu$,$\mu$p)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 $\times$
10$^{19}$ 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 $\pm$ 0.76stat $\pm$ 1.29sys) $\times$
10$^{-38}$cm$^2$, 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.
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.
