Current Status and Future Prospects of the SNO+ Experiment

Abstract

SNO+ is a large liquid scintillator-based experiment located 2 km underground at SNOLAB, Sudbury, Canada. It reuses the Sudbury Neutrino Observatory detector, consisting of a 12 m diameter acrylic vessel which will be filled with about 780 tonnes of ultra-pure liquid scintillator. Designed as a multipurpose neutrino experiment, the primary goal of SNO+ is a search for the neutrinoless double-beta decay (0νββ) of130Te. In Phase I, the detector will be loaded with 0.3% natural tellurium, corresponding to nearly 800 kg of130Te, with an expected effective Majorana neutrino mass sensitivity in the region of 55–133 meV, just above the inverted mass hierarchy. Recently, the possibility of deploying up to ten times more natural tellurium has been investigated, which would enable SNO+ to achieve sensitivity deep into the parameter space for the inverted neutrino mass hierarchy in the future. Additionally, SNO+ aims to measure reactor antineutrino oscillations, low energy solar neutrinos, and geoneutrinos, to be sensitive to supernova neutrinos, and to search for exotic physics. A first phase with the detector filled with water will begin soon, with the scintillator phase expected to start after a few months of water data taking. The0νββPhase I is foreseen for 2017.

Neutrinoless double beta decay in chiral effective field theory: lepton number violation at dimension seven

“…The observation of 0νββ would have far reaching implications: it would demonstrate that neutrinos are Majorana fermions [2], shed light on the mechanism of neutrino mass generation, and give insight on leptogenesis scenarios for the generation of the matterantimatter asymmetry in the universe [3]. The current experimental limits on the halflives are already impressive [4][5][6][7][8][9][10][11][12][13], at the level of T 0ν 1/2 > 5.3 × 10 25 y for 76 Ge [12] and T 0ν 1/2 > 1.07 × 10 26 y for 136 Xe [13], with next generation ton-scale experiments aiming at a sensitivity of T 0ν 1/2 ∼ 10 27−28 y. By itself, the observation of 0νββ would not immediately point to the underlying physical origin of LNV.…”

Physics and Commissioning of the SNO+ experiment

“…The directionality of the Cerenkov light produced is ideal for constraining γ rays from the AV, external water and PMTs. SNO+ will also set the most stringent limit on the invisible nucleon decay n → 3ν with 6 months of live-time [1].…”

“…For these advantages and others the SNO+ collaboration has constructed, and is currently commissioning, an underground LAB purification plant to produce LAB with Uranium/Thorium chain contamination of 10 −17 g U,T h /g LAB [1]. In March 2018, with commissioning complete, purified LAB will be fed into the neck of the AV replacing UPW removed by pipes at the bottom.…”

“…Crucially, the dominant natural radioactivity in this region is 214 Bi decay which can be suppressed by a factor of 5·10 5 by tagging the delayed coincidence with the 214 Po decay that follows [1].…”

Neutrinoless double beta decay

“…SNO+ [13] is a repurposing of the Sudbury Neutrino Observatory (SNO) detector for 0νβ β . A central acrylic tank in the SNO detector will be filled with liquid scintillator loaded with tellurium.…”