Abstract
Eos
is a technology demonstrator, designed to
explore the capabilities of hybrid event detection technology,
leveraging both Cherenkov and scintillation light simultaneously.
With a fiducial ...mass of four tons,
Eos
is designed to
operate in a high-precision regime, with sufficient size to utilize
time-of-flight information for full event reconstruction,
flexibility to demonstrate a range of cutting edge technologies, and
simplicity of design to facilitate potential future deployment at
alternative sites. Results from
Eos
can inform the design
of future neutrino detectors for both fundamental physics and
nonproliferation applications. This paper describes the conceptual
design and potential applications of the
Eos
detector.
A method has been developed to load tellurium into liquid scintillator so as to permit searches for neutrinoless double beta decay with high sensitivity. The approach involves the synthesis of an ...oil-soluble tellurium compound from telluric acid and an organic diol. The process utilises distillable chemicals that can be safely handled underground and affords low radioactive backgrounds, low optical absorption and high light yields at loading levels of at least several percent Te by weight.
Here, 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.
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.
The SNO+ Collaboration reports the first evidence of reactor antineutrinos in a Cherenkov detector. The nearest nuclear reactors are located 240 km away in Ontario, Canada. This analysis uses events ...with energies lower than in any previous analysis with a large water Cherenkov detector. Two analytical methods are used to distinguish reactor antineutrinos from background events in 190 days of data and yield consistent evidence for antineutrinos with a combined significance of 3.5σ.
Abstract
A liquid scintillator consisting of linear alkylbenzene as the solvent and 2,5-diphenyloxazole as the fluor was developed for the SNO+ experiment.
This mixture was chosen as it is compatible ...with acrylic and has a competitive light yield to pre-existing liquid scintillators while conferring other advantages including longer attenuation lengths, superior safety characteristics, chemical simplicity, ease of handling, and logistical availability.
Its properties have been extensively characterized and are presented here.
This liquid scintillator is now used in several neutrino physics experiments in addition to SNO+.
The SNO+ detector operated initially as a water Cherenkov detector. The
implementation of a sealed covergas system midway through water data taking
resulted in a significant reduction in the activity ...of $^{222}$Rn daughters in
the detector and allowed the lowest background to the solar electron scattering
signal above 5 MeV achieved to date. This paper reports an updated SNO+ water
phase $^8$B solar neutrino analysis with a total livetime of 282.4 days and an
analysis threshold of 3.5 MeV. The $^8$B solar neutrino flux is found to be
$\left(2.32^{+0.18}_{-0.17}\text{(stat.)}^{+0.07}_{-0.05}\text{(syst.)}\right)\times10^{6}$
cm$^{-2}$s$^{-1}$ assuming no neutrino oscillations, or
$\left(5.36^{+0.41}_{-0.39}\text{(stat.)}^{+0.17}_{-0.16}\text{(syst.)}
\right)\times10^{6}$ cm$^{-2}$s$^{-1}$ assuming standard neutrino oscillation
parameters, in good agreement with both previous measurements and Standard
Solar Model Calculations. The electron recoil spectrum is presented above 3.5
MeV.
The SNO+ collaboration reports its first spectral analysis of long-baseline
reactor antineutrino oscillation using 114 tonne-years of data. Fitting the
neutrino oscillation probability to the ...observed energy spectrum yields
constraints on the neutrino mass-squared difference $\Delta m^2_{21}$. In the
ranges allowed by previous measurements, the best-fit $\Delta m^2_{21}$ is
(8.85$^{+1.10}_{-1.33}$) $\times$ 10$^{-5}$ eV$^2$. This measurement is
continuing in the next phases of SNO+ and is expected to surpass the present
global precision on $\Delta m^2_{21}$ with about three years of data.
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