Search

A class of extensions of the Standard Model allows Lorentz and $CPT$ violations, which can be identified by the observation of sidereal modulations in the neutrino interaction rate. A search for such modulations was performed using the T2K on-axis near detector. Two complementary methods were used in this study, both of which resulted in no evidence of a signal. Limits on associated Lorentz and $CPT$-violating terms from the Standard Model extension have been derived by taking into account their correlations in this model for the first time. These results imply such symmetry violations are suppressed by a factor of more than $10^{20}$ at the GeV scale.

We perform a search for light sterile neutrinos using the data from the T2K far detector at a baseline of 295 km, with an exposure of $14.7(7.6)\times {10}^{20}$ protons on target in neutrino (antineutrino) mode. A selection of neutral-current interaction samples is also used to enhance the sensitivity to sterile mixing. No evidence of sterile neutrino mixing in the $3+1$ model was found from a simultaneous fit to the charged-current muon, electron and neutral-current neutrino samples. We set the most stringent limit on the sterile oscillation amplitude ${\sin }^2{\theta }_{24}$ for the sterile neutrino mass splitting $\mathrm{\Delta }{m}_{41}^2<3\times {10}^{-3}{\mathrm{eV}}^2/c^4$.

The T2K off-axis near detector, ND280, is used to make the first differential cross section measurements of muon neutrino charged current single positive pion production on a water target at energies $\sim 0.8\mathrm{GeV}$. The differential measurements are presented as a function of the muon and pion kinematics, in the restricted phase space defined by $p_{{\pi }^{+}}>200\mathrm{MeV}/c$, $p_{\mu }>200\mathrm{MeV}/c$, $\cos ({\theta }_{{\pi }^{+}})>0.3$ and $\cos ({\theta }_{\mu })>0.3$. The total flux integrated ${\nu }_{\mu }$ charged current single positive pion production cross section on water in the restricted phase space is measured to be $⟨\sigma {⟩}_{\varphi }=4.25\pm 0.48(\mathrm{stat})\pm 1.56(\mathrm{syst})\times {10}^{-40}{\mathrm{cm}}^2/\text{nucleon}$. The total cross section is consistent with the NEUT prediction ($5.03\times {10}^{-40}{\mathrm{cm}}^2/\text{nucleon}$) and $2\sigma$ lower than the GENIE prediction ($7.68\times {10}^{-40}{\mathrm{cm}}^2/\text{nucleon}$). The differential cross sections are in good agreement with the NEUT generator. The GENIE simulation reproduces well the shapes of the distributions, but overestimates the overall cross section normalization.

T2K reports its first results in the search for $CP$ violation in neutrino oscillations using appearance and disappearance channels for neutrino- and antineutrino-mode beams. The data include all runs from January 2010 to May 2016 and comprise $7.482\times 10^{20}$ protons on target in neutrino mode, which yielded in the far detector 32 $e$-like and $135\mu$-like events, and $7.471\times 10^{20}$ protons on target in antineutrino mode, which yielded 4 $e$-like and $66\mu$-like events. Reactor measurements of ${\sin }^{2}2{\theta }_{13}$ have been used as an additional constraint. The one-dimensional confidence interval at 90% for the phase ${\delta }_{CP}$ spans the range ($-3.13$, $-0.39$) for normal mass ordering. The $CP$ conservation hypothesis (${\delta }_{CP}=0$, $\pi$) is excluded at 90% C.L.

We present the measurement of ${\pi }^{+}$-argon inelastic cross sections using the ProtoDUNE single-phase liquid argon time projection chamber in the incident ${\pi }^{+}$ kinetic energy range of 500–800 MeV in multiple exclusive channels (absorption, charge exchange, and the remaining inelastic interactions). The results of this analysis are important inputs to simulations of liquid argon neutrino experiments such as the Deep Underground Neutrino Experiment and the Short Baseline Neutrino program at Fermi National Accelerator Laboratory. They will be employed to improve the modeling of final state interactions within neutrino event generators used by these experiments, as well as the modeling of ${\pi }^{+}$-argon secondary interactions within the liquid argon. This is the first measurement of ${\pi }^{+}$-argon absorption at this kinetic energy range as well as the first ever measurement of ${\pi }^{+}$-argon charge exchange.

A search is performed for supernovalike neutrino interactions coincident with 76 gravitational wave events detected by the LIGO/Virgo Collaboration. For 40 of these events, full readout of the time around the gravitational wave is available from the NOvA Far Detector. For these events, we set limits on the fluence of the sum of all neutrino flavors of $F<7(4)\times {10}^{10}{\mathrm{cm}}^{-2}$ at 90% C.L. assuming energy and time distributions corresponding to the Garching supernova models with masses $9.6(27){\mathrm{M}}_{\odot }$. Under the hypothesis that any given gravitational wave event was caused by a supernova, this corresponds to a distance of $r>29(50)\mathrm{kpc}$ at 90% C.L. Weaker limits are set for other gravitational wave events with partial Far Detector data and/or Near Detector data.

We report a measurement of cross section $\sigma ({\nu }_{\mu }+\text{nucleus}\to {\mu }^{-}+X)$ and the first measurements of the cross section $\sigma ({\overline{\nu }}_{\mu }+\text{nucleus}\to {\mu }^{+}+X)$ and their ratio $R(\frac{\sigma (\overline{\nu })}{\sigma (\nu )})$ at (anti) neutrino energies below 1.5 GeV. We determine the single momentum bin cross section measurements, averaged over the T2K $\overline{\nu }/\nu$-flux, for the detector target material (mainly carbon, oxygen, hydrogen and copper) with phase space restricted laboratory frame kinematics of ${\theta }_{\mu }<32°$ and $p_{\mu }>500\mathrm{MeV}/c$. The results are $\sigma (\overline{\nu })=(0.900\pm 0.029(\mathrm{stat})\pm 0.088(\mathrm{syst}))\times {10}^{-39}$ and $\sigma (\nu )=(2.41\pm 0.022(\mathrm{stat})\pm 0.231(\mathrm{syst}))\times {10}^{-39}$ in units of ${\mathrm{cm}}^2/\mathrm{nucleon}$ and $R(\frac{\sigma (\overline{\nu })}{\sigma (\nu )})=0.373\pm 0.012(\mathrm{stat})\pm 0.015(\mathrm{syst})$.

NOvA is a long-baseline neutrino oscillation experiment that measures oscillations in charged-current ${\nu }_{\mu }\to {\nu }_{\mu }$ (disappearance) and ${\nu }_{\mu }\to {\nu }_e$ (appearance) channels, and their antineutrino counterparts, using neutrinos of energies around 2 GeV over a distance of 810 km. In this work we reanalyze the dataset first examined in our previous paper [Phys. Rev. D 106, 032004 (2022)] using an alternative statistical approach based on Bayesian Markov chain Monte Carlo. We measure oscillation parameters consistent with the previous results. We also extend our inferences to include the first NOvA measurements of the reactor mixing angle ${\theta }_{13}$, where we find $0.071\le {\sin }^{2}2{\theta }_{13}\le 0.107$, and the Jarlskog invariant, where we observe no significant preference for the $CP$-conserving value $J=0$ over values favoring $CP$ violation. We use these results to examine the effects of constraints from short-baseline measurements of ${\theta }_{13}$ using antineutrinos from nuclear reactors when making NOvA measurements of ${\theta }_{23}$. Our long-baseline measurement of ${\theta }_{13}$ is shown to be consistent with the reactor measurements, supporting the general applicability and robustness of the Pontecorvo-Maki-Nakagawa-Sakata framework for neutrino oscillations.

We report a measurement of the flux-integrated cross section for inclusive muon neutrino charged-current interactions on carbon. The double-differential measurements are given as a function of the muon momentum and angle. Relative to our previous publication on this topic, these results have an increased angular acceptance and higher statistics. The data sample presented here corresponds to $5.7\times {10}^{20}$ protons on target. The total flux-integrated cross section is measured to be $(6.950\pm 0.662)\times {10}^{-39}{\mathrm{cm}}^2{\text{nucleon}}^{-1}$ and is consistent with our simulation.

The single ${\pi }^0$ production rate in neutral current neutrino interactions on water in a neutrino beam with a peak neutrino energy of 0.6 GeV has been measured using the PØD, one of the subdetectors of the T2K near detector. The production rate was measured for data taking periods when the PØD contained water ($2.64\times {10}^{20}$ protons-on-target) and also periods without water ($3.49\times {10}^{20}$ protons-on-target). A measurement of the neutral current single ${\pi }^0$ production rate on water is made using appropriate subtraction of the production rate with water in from the rate with water out of the target region. The subtraction analysis yields $106\pm 41\pm 69$ signal events where the uncertainties are statistical (stat.) and systematic (sys.) respectively. This is consistent with the prediction of 157 events from the nominal simulation. The measured to expected ratio is $0.68\pm 0.26(\mathrm{stat})\pm 0.44(\mathrm{sys})\pm 0.12(\mathrm{flux})$. The nominal simulation uses a flux integrated cross section of $7.63\times {10}^{-39}{\mathrm{cm}}^2$ per nucleon with an average neutrino interaction energy of 1.3 GeV.

The determination of the direction of a stellar core collapse via its neutrino emission is crucial for the identification of the progenitor for a multimessenger follow-up. A highly effective method of reconstructing supernova directions within the Deep Underground Neutrino Experiment (DUNE) is introduced. The supernova neutrino pointing resolution is studied by simulating and reconstructing electron-neutrino charged-current absorption on ${}^{40}\mathrm{Ar}$ and elastic scattering of neutrinos on electrons. Procedures to reconstruct individual interactions, including a newly developed technique called “brems flipping,” as well as the burst direction from an ensemble of interactions are described. Performance of the burst direction reconstruction is evaluated for supernovae happening at a distance of 10 kpc for a specific supernova burst flux model. The pointing resolution is found to be 3.4 degrees at 68% coverage for a perfect interaction-channel classification and a fiducial mass of 40 kton, and 6.6 degrees for a 10 kton fiducial mass respectively. Assuming a 4% rate of charged-current interactions being misidentified as elastic scattering, DUNE’s burst pointing resolution is found to be 4.3 degrees (8.7 degrees) at 68% coverage.

We report measurements by the T2K experiment of the parameters ${\theta }_{23}$ and $\mathrm{\Delta }{m}_{32}^2$ governing the disappearance of muon neutrinos and antineutrinos in the three-flavor neutrino oscillation model. Utilizing the ability of the experiment to run with either a mainly neutrino or a mainly antineutrino beam, the parameters are measured separately for neutrinos and antineutrinos. Using $7.482\times 10^{20}$ POT in neutrino running mode and $7.471\times 10^{20}$ POT in antineutrino mode, T2K obtained ${\sin }^2({\theta }_{23})=0.51_{-0.07}^{+0.08}$ and $\mathrm{\Delta }{m}_{32}^2=2.53_{-0.13}^{+0.15}\times {10}^{-3}{\mathrm{eV}}^2/{\mathrm{c}}^4$ for neutrinos, and ${\sin }^2({\overline{\theta }}_{23})=0.42_{-0.07}^{+0.25}$ and ${\mathrm{\Delta }{\overline{m}}^2}_{32}=2.55_{-0.27}^{+0.33}\times {10}^{-3}{\mathrm{eV}}^2/{\mathrm{c}}^4$ for antineutrinos (assuming normal mass ordering). No significant differences between the values of the parameters describing the disappearance of muon neutrinos and antineutrinos were observed.

We present new ${\nu }_{\mu }\to {\nu }_e$, ${\nu }_{\mu }\to {\nu }_{\mu }$, ${\overline{\nu }}_{\mu }\to {\overline{\nu }}_e$, and ${\overline{\nu }}_{\mu }\to {\overline{\nu }}_{\mu }$ oscillation measurements by the NOvA experiment, with a 50% increase in neutrino-mode beam exposure over the previously reported results. The additional data, combined with previously published neutrino and antineutrino data, are all analyzed using improved techniques and simulations. A joint fit to the ${\nu }_e$, ${\nu }_{\mu }$, ${\overline{\nu }}_e$, and ${\overline{\nu }}_{\mu }$ candidate samples within the 3-flavor neutrino oscillation framework continues to yield a best-fit point in the normal mass ordering and the upper octant of the ${\theta }_{23}$ mixing angle, with $\mathrm{\Delta }{m}_{32}^2=(2.41\pm 0.07)\times {10}^{-3}{\mathrm{eV}}^2$ and ${\sin }^2{\theta }_{23}=0.57_{-0.04}^{+0.03}$. The data disfavor combinations of oscillation parameters that give rise to a large asymmetry in the rates of ${\nu }_e$ and ${\overline{\nu }}_e$ appearance. This includes values of the charge parity symmetry (CP) violating phase in the vicinity of ${\delta }_{\mathrm{CP}}=\pi /2$ which are excluded by $>3\sigma$ for the inverted mass ordering, and values around ${\delta }_{\mathrm{CP}}=3\pi /2$ in the normal ordering which are disfavored at $2\sigma$ confidence.

The inclusive electron neutrino charged-current cross section is measured in the NOvA near detector using $8.02\times {10}^{20}$ protons-on-target in the NuMI beam. The sample of GeV electron neutrino interactions is the largest analyzed to date and is limited by $\simeq 17\%$ systematic rather than the $\simeq 7.4\%$ statistical uncertainties. The double-differential cross section in final-state electron energy and angle is presented for the first time, together with the single-differential dependence on $Q^2$ (squared four-momentum transfer) and energy, in the range $1\mathrm{GeV}\le E_{\nu }<6\mathrm{GeV}$. Detailed comparisons are made to the predictions of the GENIE, GiBUU, NEUT, and NuWro neutrino event generators. The data do not strongly favor a model over the others consistently across all three cross sections measured, though some models have especially good or poor agreement in the single differential cross section vs $Q^2$.

A primary goal of the upcoming Deep Underground Neutrino Experiment (DUNE) is to measure the $\mathcal{O}(10)\mathrm{MeV}$ neutrinos produced by a Galactic core-collapse supernova if one should occur during the lifetime of the experiment. The liquid-argon-based detectors planned for DUNE are expected to be uniquely sensitive to the ${\nu }_e$ component of the supernova flux, enabling a wide variety of physics and astrophysics measurements. A key requirement for a correct interpretation of these measurements is a good understanding of the energy-dependent total cross section $\sigma (E_{\nu })$ for charged-current ${\nu }_e$ absorption on argon. In the context of a simulated extraction of supernova ${\nu }_e$ spectral parameters from a toy analysis, we investigate the impact of $\sigma (E_{\nu })$ modeling uncertainties on DUNE’s supernova neutrino physics sensitivity for the first time. We find that the currently large theoretical uncertainties on $\sigma (E_{\nu })$ must be substantially reduced before the ${\nu }_e$ flux parameters can be extracted reliably; in the absence of external constraints, a measurement of the integrated neutrino luminosity with less than 10% bias with DUNE requires $\sigma (E_{\nu })$ to be known to about 5%. The neutrino spectral shape parameters can be known to better than 10% for a 20% uncertainty on the cross-section scale, although they will be sensitive to uncertainties on the shape of $\sigma (E_{\nu })$. A direct measurement of low-energy ${\nu }_e$-argon scattering would be invaluable for improving the theoretical precision to the needed level.

This paper reports measurements of final-state proton multiplicity, muon and proton kinematics, and their correlations in charged-current pionless neutrino interactions, measured by the T2K ND280 near detector in its plastic scintillator (${\mathrm{C}}_8{\mathrm{H}}_8$) target. The data were taken between years 2010 and 2013, corresponding to approximately $6\times {10}^{20}$ protons on target. Thanks to their exploration of the proton kinematics and of imbalances between the proton and muon kinematics, the results offer a novel probe of the nuclear-medium effects most pertinent to the (sub-)GeV neutrino-nucleus interactions that are used in accelerator-based long-baseline neutrino oscillation measurements. These results are compared to many neutrino-nucleus interaction models which all fail to describe at least part of the observed phase space. In case of events without a proton above a detection threshold in the final state, a fully consistent implementation of the local Fermi gas model with multinucleon interactions gives the best description of the data. In the case of at least one proton in the final state, the spectral function model agrees well with the data, most notably when measuring the kinematic imbalance between the muon and the proton in the plane transverse to the incoming neutrino. Within the models considered, only the existence of multinucleon interactions are able to describe the extracted cross section within regions of high transverse kinematic imbalance. The effect of final-state interactions is also discussed.

The T2K experiment measures muon neutrino disappearance and electron neutrino appearance in accelerator-produced neutrino and antineutrino beams. With an exposure of $14.7(7.6)\times {10}^{20}$ protons on target in the neutrino (antineutrino) mode, 89 ${\nu }_e$ candidates and seven anti-${\nu }_e$ candidates are observed, while 67.5 and 9.0 are expected for ${\delta }_{CP}=0$ and normal mass ordering. The obtained $2\sigma$ confidence interval for the $CP$-violating phase, ${\delta }_{CP}$, does not include the $CP$-conserving cases (${\delta }_{CP}=0$, $\pi$). The best-fit values of other parameters are ${\sin }^2{\theta }_{23}=0.526_{-0.036}^{+0.032}$ and $\mathrm{\Delta }{m}_{32}^2={2.463}_{-0.070}^{+0.071}\times {10}^{-3}{\mathrm{eV}}^2/c^4$.

We report the first measurement of the flux-averaged cross section for charged current coherent ${\pi }^{+}$ production on carbon for neutrino energies less than 1.5 GeV, and with a restriction on the final state phase space volume in the T2K near detector, ND280. Comparisons are made with predictions from the Rein-Sehgal coherent production model and the model by Alvarez-Ruso et al., the latter representing the first implementation of an instance of the new class of microscopic coherent models in a neutrino interaction Monte Carlo event generator. We observe a clear event excess above background, disagreeing with the null results reported by K2K and SciBooNE in a similar neutrino energy region. The measured flux-averaged cross sections are below those predicted by both the Rein-Sehgal and Alvarez-Ruso et al. models.

ProtoDUNE Single-Phase (ProtoDUNE-SP) is a 770-ton liquid argon time projection chamber that operated in a hadron test beam at the CERN Neutrino Platform in 2018. We present a measurement of the total inelastic cross section of charged kaons on argon as a function of kaon energy using 6 and $7\mathrm{GeV}/c$ beam momentum settings. The flux-weighted average of the extracted inelastic cross section at each beam momentum setting was measured to be $380\pm 26\mathrm{mbarns}$ for the $6\mathrm{GeV}/c$ setting and $379\pm 35\mathrm{mbarns}$ for the $7\mathrm{GeV}/c$ setting.

Neutrino-nucleus cross section measurements are critical for future neutrino oscillation analyses. However, our models to describe them require further refinement, and a deeper understanding of the underlying physics is essential for future neutrino oscillation experiments to realize their ambitious physics goals. Current neutrino cross section measurements provide clear deficiencies in neutrino interaction modeling, but almost all are reported averaged over broad neutrino fluxes, rendering their interpretation challenging. Using the concept of deep underground neutrino experiment-precision reaction independent spectrum measurement (DUNE-PRISM)—a movable near detector that samples multiple off axis positions—neutrino interaction measurements can be used to construct narrow virtual fluxes (less than 100 MeV wide). These fluxes can be used to extract charged-current neutrino-nucleus cross sections as functions of outgoing lepton kinematics within specific neutrino energy ranges. Based on a dedicated simulation with realistic event statistics and flux-related systematic uncertainties, but assuming an almost-perfect detector, we run a feasibility study demonstrating how DUNE-PRISM data can be used to measure muon neutrino charged-current integrated and differential cross sections over narrow fluxes. We find that this approach enables a largely model-independent reconstruction of powerful observables, including energy transfer, typically accessible only in electron scattering measurements, but that large exposures may be required for differential cross section measurements with few-percentage statistical uncertainties.