We report the first measurement of coherent elastic neutrino-nucleus scattering (CEvNS) on argon using a liquid argon detector at the Oak Ridge National Laboratory Spallation Neutron Source. Two ...independent analyses prefer CEvNS over the background-only null hypothesis with greater than 3σ significance. The measured cross section, averaged over the incident neutrino flux, is (2.2±0.7)×10^{-39} cm^{2}-consistent with the standard model prediction. The neutron-number dependence of this result, together with that from our previous measurement on CsI, confirms the existence of the CEvNS process and provides improved constraints on nonstandard neutrino interactions.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
The coherent elastic scattering of neutrinos off nuclei has eluded detection for four decades, even though its predicted cross section is by far the largest of all low-energy neutrino couplings. This ...mode of interaction offers new opportunities to study neutrino properties and leads to a miniaturization of detector size, with potential technological applications. We observed this process at a 6.7σ̃ confidence level, using a low-background, 14.6-kilogram CsINa scintillator exposed to the neutrino emissions from the Spallation Neutron Source at Oak Ridge National Laboratory. Characteristic signatures in energy and time, predicted by the standard model for this process, were observed in high signal-to-background conditions. Improved constraints on nonstandard neutrino interactions with quarks are derived from this initial data set.
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BFBNIB, NMLJ, NUK, ODKLJ, PNG, SAZU, UL, UM, UPUK
Abstract
We present the analysis and results of the first dataset
collected with the MARS neutron detector
deployed at the Oak Ridge National
Laboratory Spallation Neutron Source (SNS) for the ...purpose of
monitoring and characterizing the beam-related neutron (BRN) background
for the COHERENT collaboration. MARS was positioned
next to the COH-CsI coherent elastic neutrino-nucleus scattering detector
in the SNS basement corridor. This is the basement location of
closest proximity to the SNS target and thus, of highest neutrino flux,
but it is also well shielded from the BRN flux by infill concrete
and gravel. These data show the detector registered roughly one BRN per day.
Using MARS' measured detection efficiency, the incoming
BRN flux is estimated to be 1.20 ± 0.56 neutrons/m^2/MWh
for neutron energies above ∼3.5 MeV and up to a few tens of MeV.
We compare our results with previous BRN measurements in the SNS basement corridor
reported by other neutron detectors.
The COHERENT Collaboration searched for scalar dark matter particles produced at the Spallation Neutron Source with masses between 1 and 220 MeV/c^{2} using a CsINa scintillation detector sensitive ...to nuclear recoils above 9 keV_{nr}. No evidence for dark matter is found and we thus place limits on allowed parameter space. With this low-threshold detector, we are sensitive to coherent elastic scattering between dark matter and nuclei. The cross section for this process is orders of magnitude higher than for other processes historically used for accelerator-based direct-detection searches so that our small, 14.6 kg detector significantly improves on past constraints. At peak sensitivity, we reject the flux consistent with the cosmologically observed dark-matter concentration for all coupling constants α_{D}<0.64, assuming a scalar dark-matter particle. We also calculate the sensitivity of future COHERENT detectors to dark-matter signals which will ambitiously test multiple dark-matter spin scenarios.
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We report on the technical design and expected performance of a 592 kg heavy-water-Cherenkov detector to measure the absolute neutrino flux from the pion-decay-at-rest neutrino source at the ...Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). The detector will be located roughly 20 m from the SNS target and will measure the neutrino flux with better than 5% statistical uncertainty in 2 years. This heavy-water detector will serve as the first module of a two-module detector system to ultimately measure the neutrino flux to 2–3% at both the First Target Station and the planned Second Target Station of the SNS. This detector will significantly reduce a dominant systematic uncertainty for neutrino cross-section measurements at the SNS, increasing the sensitivity of searches for new physics.
Abstract
We present results of several measurements of CsINa
scintillation response to 3–60 keV energy nuclear recoils
performed by the COHERENT collaboration using tagged neutron elastic
scattering ...experiments and an endpoint technique. Earlier results,
used to estimate the coherent elastic neutrino-nucleus scattering
(CEvNS) event rate for the first observation of this process
achieved by COHERENT at the Spallation Neutron Source (SNS), have
been reassessed. We discuss corrections for the identified
systematic effects and update the respective uncertainty values. The
impact of updated results on future precision tests of CEvNS is
estimated. We scrutinize potential systematic effects that could
affect each measurement. In particular we confirm the response of
the H11934-200 Hamamatsu photomultiplier tube (PMT) used for the
measurements presented in this study to be linear in the relevant
signal scale region.
Using an 185-kg NaITl array, COHERENT has measured the inclusive electron-neutrino charged-current cross section on ^{127}I with pion decay-at-rest neutrinos produced by the Spallation Neutron Source ...at Oak Ridge National Laboratory. Iodine is one the heaviest targets for which low-energy (≤50 MeV) inelastic neutrino-nucleus processes have been measured, and this is the first measurement of its inclusive cross section. After a five-year detector exposure, COHERENT reports a flux-averaged cross section for electron neutrinos of 9.2_{-1.8}^{+2.1}×10^{-40} cm^{2}. This corresponds to a value that is ∼41% lower than predicted using the MARLEY event generator with a measured Gamow-Teller strength distribution. In addition, the observed visible spectrum from charged-current scattering on ^{127}I has been measured between 10 and 55 MeV, and the exclusive zero-neutron and one-or-more-neutron emission cross sections are measured to be 5.2_{-3.1}^{+3.4}×10^{-40} and 2.2_{-0.5}^{+0.4}×10^{-40} cm^{2}, respectively.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
We report on the preparation of and calibration measurements with a 83mKr source for the CENNS-10 liquid argon detector. 83mKr atoms generated in the decay of a 83Rb source were introduced into the ...detector via injection into the Ar circulation loop. Scintillation light arising from the 9.4 keV and 32.1 keV conversion electrons in the decay of 83mKr in the detector volume were then observed. This calibration source allows the characterization of the low-energy response of the CENNS-10 detector and is applicable to other low-energy-threshold detectors. The energy resolution of the detector was measured to be 9% at the total 83mKr decay energy of 41.5 keV. We performed an analysis to separately calibrate the detector using the two conversion electrons at 9.4 keV and 32.1 keV.
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