SNO+ will soon enter its first phase of physics data-taking. The Canadian-based detector forms part of the SNOLAB underground facility, in a Sudbury nickel mine; its location providing more than two ...kilometres of rock overburden. We present an overview of the SNO+ experiment and its physics capabilities. Our primary goal is the search for neutrinoless double-beta decay, where our expected sensitivity would place an upper limit of 1.9 × 1026 y, at 90% CL, on the half-life of neutrinoless double-beta decay in 130Te. We also intend to build on the success of SNO by studying the solar neutrino spectrum. In the unloaded scintillator phase SNO+ has the ability to make precision measurements of the fluxes of low-energy pep neutrinos and neutrinos from the CNO cycle. Other physics goals include: determining the spectrum of reactor antineutrinos, to further constrain Δ m 12 2 ; detecting neutrinos produced by a galactic supernova and investigating certain modes of nucleon decay.
Background Analysis for the SNO+ Experiment Wilson, J.R.; Langrock, S.; Arushanova, E. ...
Journal of physics. Conference series,
09/2017, Letnik:
888, Številka:
1
Journal Article
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SNO+ aims to conduct a world leading search for neutrino-less double beta decay of 130Te with a 5 year half-life sensitivity of 1.9×1026 years using 3.9 tonnes of natural Tellurium isotropically ...loaded in 780 tonnes of liquid scintillator. The total background budget within 0.5σ to 1.5σ of the 0νββ energy is 13.4 events per year, dominated by 8B solar neutrinos. We discuss SNO+ analysis strategies to measure the residual Uranium and Thorium chain backgrounds through the timing coincidence of short half-life components 214Bi - 214Po and 212Bi - 212Po. We show that these so-called Bi-Po events can be rejected from the 0νββ region of interest (ROI) with 99.995% efficiency and minimal (<2%) signal sacrifice. Pure samples of Bi-Pos can also be created to accurately measure the rates of Uranium and Thorium decays in-situ. In a fraction of decays, the Polonium alpha decay will occur within the same trigger window as the beta, resulting in a higher energy 'pile-up' event. Separate classifications based on the hit timing structure efficiency reject these events with minimal (<1%) signal loss. A final class of background events results from the pile up of higher frequency low energy backgrounds with events such as 2νββ, which would not otherwise contribute to the ROI. We present a final set of of event classifiers developed specifically to reject these events and show that their contribution to the double beta analysis can be reduced to negligible levels.
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.
SNO+ is a multi-purpose liquid scintillator detector with the main aim of investigating neutrinoless double beta decay (0 2 ) of 130Te. The sensitivity of such rare decay searches is limited by ...backgrounds, therefore it is crucial to reduce and constrain backgrounds in the energy region of interest (ROI). This thesis presents the comprehensive study of particularly dangerous pileup backgrounds occurring in the scintillator with 0.3% of Tellurium-130 loading. The thesis determines which pileup backgrounds are the most problematic, estimates their event levels, describes their properties and methods to reject them from the ROI of 0 2 . To show the vital importance of this analysis, the thesis demonstrates the improvement of the sensitivity to the 130Te(0 2 ) half-life by 32%. This thesis presents the Channel Software Status (CSS) framework which has been developed to check the performance of each photomultiplier tube (PMT). It is one component of a processing pipeline that is crucial to ensuring the SNO+ experiment takes quality data. The framework has been tested on the air-fill data and is ready for further tuning using the stable water data. SNO+ has an extensive calibration program, including a proposed 90Y -emitting calibration source. This thesis outlines the benefits of using such a source to test the position and energy resolutions across the energy region spread up to 2.28 MeV. The thesis describes the design of the source and the manufacturing procedure. The performed tests demonstrated the promising potential for using 90Y to study properties of scintillators.
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