Used for both proton decay searches and neutrino physics, large water Cherenkov (WC) detectors have been very successful tools in particle physics. They are notable for their large masses and charged ...particle detection capabilities. While current WC detectors reconstruct charged particle tracks over a wide energy range, they cannot efficiently detect neutrons. Gadolinium (Gd) has the largest thermal neutron capture cross section of all stable nuclei and produces an 8 MeV gamma cascade that can be detected with high efficiency. Because of the many new physics opportunities that neutron tagging with a Gd salt dissolved in water would open up, a large-scale R&D program called EGADS was established to demonstrate this technique’s feasibility. EGADS features all the components of a WC detector, chiefly a 200-ton stainless steel water tank furnished with 240 photo-detectors, DAQ, and a water system that removes all impurities from water while keeping Gd in solution. In this paper we discuss the milestones towards demonstrating the feasibility of this novel technique, and the features of EGADS in detail.
First gadolinium loading to Super-Kamiokande Hiraide, K.; Imaizumi, S.; Moriyama, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2022, Letnik:
1027
Journal Article
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In order to improve Super-Kamiokande’s neutron detection efficiency and to thereby increase its sensitivity to the diffuse supernova neutrino background flux, 13 tons of Gd2(SO4)3⋅8H2O (gadolinium ...sulfate octahydrate) was dissolved into the detector’s otherwise ultrapure water from July 14 to August 17, 2020, marking the start of the SK-Gd phase of operations. During the loading, water was continuously recirculated at a rate of 60 m3/h, extracting water from the top of the detector and mixing it with concentrated Gd2(SO4)3⋅8H2O solution to create a 0.02% solution of the Gd compound before injecting it into the bottom of the detector. A clear boundary between the Gd-loaded and pure water was maintained through the loading, enabling monitoring of the loading itself and the spatial uniformity of the Gd concentration over the 35 days it took to reach the top of the detector. During the subsequent commissioning the recirculation rate was increased to 120 m3/h, resulting in a constant and uniform distribution of Gd throughout the detector and water transparency equivalent to that of previous pure-water operation periods. Using an Am–Be neutron calibration source the mean neutron capture time was measured to be 115±1 μs, which corresponds to a Gd concentration of 111±2 ppm, as expected for this level of Gd loading. This paper describes changes made to the water circulation system for this detector upgrade, the Gd loading procedure, detector commissioning, and the first neutron calibration measurements in SK-Gd.
With the Main Injector Neutrino Oscillation Search (MINOS) experiment decommissioned, muon and hadron monitors became an important diagnostic tool for the NuMI Off-axis vμ Appearance (NOvA) ...experiment at Fermilab to monitor the Neutrinos at the Main Injector (NuMI) beam. The goal of this study is to maintain the quality of the monitor signals and to establish correlations with the neutrino beam profile. And we carry out a systematic study of the response of the muon monitors to the changes in the parameters of the proton beam and lattice parameters. We report here on the progress of the beam data analysis and comparison with the simulation results.
The inclusive electron neutrino charged-current cross section is measured in the NOvA near detector using 8.02 x 1020 protons-on-target (POT) in the NuMI beam. The sample of GeV electron neutrino ...interactions is the largest analyzed to date and is limited by ≃ 17% systematic rather than the ≃ 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 Q2 (squared four-momentum transfer) and energy, in the range 1 GeV ≤ Eν < 6 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. Q2.
NOvA is a long-baseline neutrino oscillation experiment that measures oscillations in charged-current ν μ → ν μ (disappearance) and ν μ → ν 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 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 θ 13 , where we find 0.071 ≤ sin 2 2 θ 13 ≤ 0.107 , and the Jarlskog invariant, where we observe no significant preference for the C P -conserving value J = 0 over values favoring C P violation. We use these results to examine the effects of constraints from short-baseline measurements of θ 13 using antineutrinos from nuclear reactors when making NOvA measurements of θ 23 . Our long-baseline measurement of θ 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. Published by the American Physical Society 2024
Radioactivity induced by cosmic muon spallation is a dominant source of backgrounds for O ( 10 MeV ) neutrino interactions in water Cherenkov detectors. In particular, it is crucial to reduce ...backgrounds to measure the solar neutrino spectrum and find neutrino interactions from distant supernovae. In this paper we introduce new techniques to locate muon-induced hadronic showers and efficiently reject spallation backgrounds. Applying these techniques to the solar neutrino analysis with an exposure of 2790 × 22.5 kton · day increases the signal efficiency by 12.6%, approximately corresponding to an additional year of detector running. Furthermore, we present the first spallation simulation at Super-Kamiokande, where we model hadronic interactions using . The agreement between the isotope yields and shower pattern in this simulation and in the data gives confidence in the accuracy of this simulation, and thus opens the door to use it to optimize muon spallation removal in new data with gadolinium-enhanced neutron capture detection. Published by the American Physical Society 2024
We report cross-section measurements of the final-state muon kinematics for vu charged-current interactions in the NOvA near detector using an accumulated 8.09 x 1020 protons on target 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, Ev, and square of the four-momentum transfer, Q2. We compare the results to inclusive cross-section predictions from various neutrino event generators via χ2 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 Q2, indicating a missing suppression of the cross section in current neutrino-nucleus scattering models.
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