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The NOvA experiment at Fermilab uses a beam of neutrinos and two detectors separated by an 810 km baseline to observe muon neutrino disappearance and electron neutrino appearance. These measurements have the potential to reveal the remaining unknowns in neutrino oscillations, namely the mass hierarchy, the 23 octant, and perhaps even hint at the violation of CP in the neutrino sector. This paper describes the current status of the NOvA experiment and present results from two years of data taking, doubling the exposure of our initial results.

The water at the proposed site of the CHIPS water Cherenkov detector has been studied to measure its attenuation length as a function of filtering time. A 3.2 m vertical column was filled with the water from the Wentworth Pit, proposed site of the CHIPS deployment. Results consistent with attenuation lengths of up to 100m have been observed at this wavelength with filtration and UV sterilization alone.

The two-detector design of the NOvA neutrino oscillation experiment, in which two functionally identical detectors are exposed to an intense neutrino beam, aids in canceling leading order effects of cross-section uncertainties. However, limited knowledge of neutrino interaction cross sections still gives rise to some of the largest systematic uncertainties in current oscillation measurements. We show contemporary models of neutrino interactions to be discrepant with data from NOvA, consistent with discrepancies seen in other experiments. Adjustments to neutrino interaction models in GENIE are presented, creating an effective model that improves agreement with our data. We also describe systematic uncertainties on these models, including uncertainties on multi-nucleon interactions from a newly developed procedure using NOvA near detector data.

The rate of high energy cosmic ray muons as measured underground is shown to be strongly correlated with upper‐air temperatures during short‐term atmospheric (10‐day) events. The effects are seen by correlating data from the MINOS underground detector and temperatures from the European Centre for Medium Range Weather Forecasts during the winter periods from 2003–2007. This effect provides an independent technique for the measurement of meteorological conditions and presents a unique opportunity to measure both short and long‐term changes in this important part of the atmosphere.

This Letter reports measurements of muon-neutrino disappearance and electron-neutrino appearance and the corresponding antineutrino processes between the two NOvA detectors in the NuMI neutrino beam. These measurements use a dataset with double the neutrino mode beam exposure that was previously analyzed, along with improved simulation and analysis techniques. A joint fit to these samples in the three-flavor paradigm results in the most precise single-experiment constraint on the atmospheric neutrino mass splitting, \\(\\Delta m^2_{32}= 2.431^{+0.036}_{-0.034} (-2.479^{+0.036}_{-0.036}) \\times 10^{-3}~\\mathrm{eV}^2\\) if the mass ordering is normal (inverted). In both orderings, a region close to maximal mixing with \\(\\sin^2 \\theta_{23}=0.55^{+0.02}_{-0.06}\\) is preferred. The NOvA data show a mild preference for the normal mass ordering with a Bayes factor of 2.4 (corresponding to 70% of the posterior probability), indicating that the normal ordering is 2.4 times more probable than the inverted ordering. When incorporating a 2D \\(\\Delta m^2_{32}\\text{--}\\sin^2 2\\theta_{13}\\) constraint based on Daya Bay data, this preference strengthens to a Bayes factor of 6.6 (87%).

The landmark discovery that neutrinos have mass and can change type (or \"flavor\") as they propagate -- a process called neutrino oscillation -- has opened up a rich array of theoretical and experimental questions being actively pursued today. Neutrino oscillation remains the most powerful experimental tool for addressing many of these questions, including whether neutrinos violate charge-parity (CP) symmetry, which has possible connections to the unexplained preponderance of matter over antimatter in the universe. Oscillation measurements also probe the mass-squared differences between the different neutrino mass states (\\(\\Delta m^2\\)), whether there are two light states and a heavier one (normal ordering) or vice versa (inverted ordering), and the structure of neutrino mass and flavor mixing. Here, we carry out the first joint analysis of data sets from NOvA and T2K, the two currently operating long-baseline neutrino oscillation experiments (hundreds of kilometers of neutrino travel distance), taking advantage of our complementary experimental designs and setting new constraints on several neutrino sector parameters. This analysis provides new precision on the \\(\\Delta m^2_{32}\\) mass difference, finding \\(2.43^{+0.04}_{-0.03}\\ \\left(-2.48^{+0.03}_{-0.04}\\right)\\times 10^{-3}~\\mathrm{eV}^2\\) in the normal (inverted) ordering, as well as a \\(3\\sigma\\) interval on \\(\\delta_{\\rm CP}\\) of \\([-1.38\\pi,\\ 0.30\\pi]\\) \\(\\left([-0.92\\pi,\\ -0.04\\pi]\\right)\\) in the normal (inverted) ordering. The data show no strong preference for either mass ordering, but notably if inverted ordering were assumed true within the three-flavor mixing paradigm, then our results would provide evidence of CP symmetry violation in the lepton sector.

NOvA is a long-baseline neutrino oscillation experiment that measures oscillations in charged-current \\(\\nu_{\\mu} \\rightarrow \\nu_{\\mu}\\) (disappearance) and \\(\\nu_{\\mu} \\rightarrow \\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}\\) and the Jarlskog invariant. We use these results to quantify the strength of our inferences about CP violation, as well as 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 also shown to be consistent with the reactor measurements, supporting the general applicability and robustness of the PMNS framework for neutrino oscillations.

We report cross-section measurements of the final-state muon kinematics for \\numu charged-current interactions in the NOvA near detector using an accumulated 8.09\\(\\times10^{20}\\) protons-on-target (POT) in the NuMI beam. We present the results as a double-differential cross section in the observed outgoing muon energy and angle, as well as single-differential cross sections in the derived neutrino energy, \\(E_\\nu\\), and square of the four-momentum transfer, \\(Q^2\\). We compare the results to inclusive cross-section predictions from various neutrino event generators via \\(\\chi^2\\) calculations using a covariance matrix that accounts for bin-to-bin correlations of systematic uncertainties. These comparisons show a clear discrepancy between the data and each of the tested predictions at forward muon angle and low \\(Q^2\\), indicating a missing suppression of the cross section in current neutrino-nucleus scattering models.

We present new \\(\\nu_\\mu\\rightarrow\\nu_e\\), \\(\\nu_\\mu\\rightarrow\\nu_\\mu\\), \\(\\overline{\\nu}_\\mu\\rightarrow\\overline{\\nu}_e\\), and \\(\\overline{\\nu}_\\mu\\rightarrow\\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 \\(\\Delta m^{2}_{32} = (2.41\\pm0.07)\\times 10^{-3}\\) eV\\(^2\\) and \\(\\sin^2\\theta_{23} = 0.57^{+0.03}_{-0.04}\\). 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 CP-violating phase in the vicinity of \\(\\delta_\\text{CP} = \\pi/2\\) which are excluded by \\(>3\\sigma\\) for the inverted mass ordering, and values around \\(\\delta_\\text{CP} = 3\\pi/2\\) in the normal ordering which are disfavored at 2\\(\\sigma\\) confidence.

This Letter reports results from the first long-baseline search for sterile antineutrinos mixing in an accelerator-based antineutrino-dominated beam. The rate of neutral-current interactions in the two NOvA detectors, at distances of 1 km and 810 km from the beam source, is analyzed using an exposure of \\(12.51\\times10^{20}\\) protons-on-target from the NuMI beam at Fermilab running in antineutrino mode. A total of \\(121\\) of neutral-current candidates are observed at the Far Detector, compared to a prediction of \\(122\\pm11\\)(stat.)\\(\\pm15\\)(syst.) assuming mixing between three active flavors. No evidence for \\(\\bar{\\nu}_{\\mu}\\rightarrow\\bar{\\nu}_{s}\\) oscillation is observed. Interpreting this result within a 3+1 model, constraints are placed on the mixing angles \\({\\theta}_{24} < 25^{\\circ}\\) and \\({\\theta}_{34} < 32^{\\circ}\\) at the 90% C.L. for \\(0.05\\)eV\\(^{2} \\leq \\Delta m^{2}_{41} \\leq 0.5\\)eV\\(^{2}\\), the range of mass splittings that produces no significant oscillations at the Near Detector. These are the first 3+1 confidence limits set using long-baseline accelerator antineutrinos.