14 research outputs found
Measurement of the 8B solar neutrino flux in SNO+ with very low backgrounds
A measurement of the 8B solar neutrino flux has been made using a 69.2 kt-day dataset acquired with the SNO+ detector during its water commissioning phase. At energies above 6 MeV the dataset is an extremely pure sample of solar neutrino elastic scattering events, owing primarily to the detector’s deep location, allowing an accurate measurement with relatively little exposure. In that energy region the best fit background rate is 0.25+0.09−0.07  events/kt−day, significantly lower than the measured solar neutrino event rate in that energy range, which is 1.03+0.13−0.12  events/kt−day. Also using data below this threshold, down to 5 MeV, fits of the solar neutrino event direction yielded an observed flux of 2.53+0.31−0.28(stat)+0.13−0.10(syst)×106  cm−2 s−1, assuming no neutrino oscillations. This rate is consistent with matter enhanced neutrino oscillations and measurements from other experiments
Observation of Antineutrinos from Distant Reactors using Pure Water at SNO+
The SNO+ collaboration reports the first observation of reactor antineutrinos
in a Cherenkov detector. The nearest nuclear reactors are located 240 km away
in Ontario, Canada. This analysis used events with energies lower than in any
previous analysis with a large water Cherenkov detector. Two analytical methods
were used to distinguish reactor antineutrinos from background events in 190
days of data and yielded consistent observations of antineutrinos with a
combined significance of 3.5 .Comment: v2: add missing author, add link to supplemental materia
Improved search for invisible modes of nucleon decay in water with the SNO+ detector
This paper reports results from a search for single and multi-nucleon
disappearance from the O nucleus in water within the \snoplus{} detector
using all of the available data. These so-called "invisible" decays do not
directly deposit energy within the detector but are instead detected through
their subsequent nuclear de-excitation and gamma-ray emission. New limits are
given for the partial lifetimes:
years, years, years,
years, and years at 90\% Bayesian
credibility level (with a prior uniform in rate). All but the () results improve on existing limits by a factor of about 3.info:eu-repo/semantics/publishedVersio
Measurement of neutron-proton capture in the SNO+ water phase
The SNO+ experiment collected data as a low-threshold water Cherenkov
detector from September 2017 to July 2019. Measurements of the 2.2-MeV
produced by neutron capture on hydrogen have been made using an Am-Be
calibration source, for which a large fraction of emitted neutrons are produced
simultaneously with a 4.4-MeV . Analysis of the delayed coincidence
between the 4.4-MeV and the 2.2-MeV capture revealed a
neutron detection efficiency that is centered around 50% and varies at the
level of 1% across the inner region of the detector, which to our knowledge is
the highest efficiency achieved among pure water Cherenkov detectors. In
addition, the neutron capture time constant was measured and converted to a
thermal neutron-proton capture cross section of mb
Search for invisible modes of nucleon decay in water with the SNO+ detector
This paper reports results from a search for nucleon decay through invisible modes, where no visible energy is directly deposited during the decay itself, during the initial water phase of SNO+. However, such decays within the oxygen nucleus would produce an excited daughter that would subsequently deexcite, often emitting detectable gamma rays. A search for such gamma rays yields limits of 2.5×1029  y at 90% Bayesian credibility level (with a prior uniform in rate) for the partial lifetime of the neutron, and 3.6×1029  y for the partial lifetime of the proton, the latter a 70% improvement on the previous limit from SNO. We also present partial lifetime limits for invisible dinucleon modes of 1.3×1028  y for nn, 2.6×1028  y for pn and 4.7×1028  y for pp, an improvement over existing limits by close to 3 orders of magnitude for the latter two
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Measurement of the B 8 solar neutrino flux in SNO+ with very low backgrounds
A measurement of the B8 solar neutrino flux has been made using a 69.2 kt-day dataset acquired with the SNO+ detector during its water commissioning phase. At energies above 6 MeV the dataset is an extremely pure sample of solar neutrino elastic scattering events, owing primarily to the detector's deep location, allowing an accurate measurement with relatively little exposure. In that energy region the best fit background rate is 0.25-0.07+0.09 events/kt-day, significantly lower than the measured solar neutrino event rate in that energy range, which is 1.03-0.12+0.13 events/kt-day. Also using data below this threshold, down to 5 MeV, fits of the solar neutrino event direction yielded an observed flux of 2.53-0.28+0.31(stat)-0.10+0.13(syst)×106 cm-2 s-1, assuming no neutrino oscillations. This rate is consistent with matter enhanced neutrino oscillations and measurements from other experiments
Mineral Detection of Neutrinos and Dark Matter. A Whitepaper
Minerals are solid state nuclear track detectors - nuclear recoils in a
mineral leave latent damage to the crystal structure. Depending on the mineral
and its temperature, the damage features are retained in the material from
minutes (in low-melting point materials such as salts at a few hundred degrees
C) to timescales much larger than the 4.5 Gyr-age of the Solar System (in
refractory materials at room temperature). The damage features from the
MeV fission fragments left by spontaneous fission of U and other heavy
unstable isotopes have long been used for fission track dating of geological
samples. Laboratory studies have demonstrated the readout of defects caused by
nuclear recoils with energies as small as keV. This whitepaper discusses
a wide range of possible applications of minerals as detectors for keV nuclear recoils: Using natural minerals, one could use the damage
features accumulated over Myr Gyr to measure astrophysical
neutrino fluxes (from the Sun, supernovae, or cosmic rays interacting with the
atmosphere) as well as search for Dark Matter. Using signals accumulated over
months to few-years timescales in laboratory-manufactured minerals, one could
measure reactor neutrinos or use them as Dark Matter detectors, potentially
with directional sensitivity. Research groups in Europe, Asia, and America have
started developing microscopy techniques to read out the nm
damage features in crystals left by keV nuclear recoils. We
report on the status and plans of these programs. The research program towards
the realization of such detectors is highly interdisciplinary, combining
geoscience, material science, applied and fundamental physics with techniques
from quantum information and Artificial Intelligence.Comment: 115 pages, many pictures of tracks. Please see the source file for
higher resolution versions of some plots. v2: matches the published versio
Improved search for invisible modes of nucleon decay in water with the SNO plus detector
This paper reports results from a search for single and multinucleon disappearance from the O16 nucleus in water within the SNO+ detector using all of the available data. These so-called "invisible"decays do not directly deposit energy within the detector but are instead detected through their subsequent nuclear deexcitation and gamma-ray emission. New limits are given for the partial lifetimes: τ(n→inv)>9.0×1029 years, τ(p→inv)>9.6×1029 years, τ(nn→inv)>1.5×1028 years, τ(np→inv)>6.0×1028 years, and τ(pp→inv)>1.1×1029 years at 90% Bayesian credibility level (with a prior uniform in rate). All but the (nn→inv) results improve on existing limits by a factor of about 3
Optical calibration of the SNO+ detector in the water phase with deployed sources
SNO+ is a large-scale liquid scintillator experiment with the primary goal of searching for neutrinoless double beta decay, and is located approximately 2 km underground in SNOLAB, Sudbury, Canada. The detector acquired data for two years as a pure water Cherenkov detector, starting in May 2017. During this period, the optical properties of the detector were measured in situ using a deployed light diffusing sphere, with the goal of improving the detector model and the energy response systematic uncertainties. The measured parameters included the water attenuation coefficients, effective attenuation coefficients for the acrylic vessel, and the angular response of the photomultiplier tubes and their surrounding light concentrators, all across different wavelengths. The calibrated detector model was validated using a deployed tagged gamma source, which showed a 0.6% variation in energy scale across the primary target volume