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The SNO+ Experiment: Overview and Status

The SNO+ Experiment: Overview and Status. DPG Spring Meeting Dresden 2013 Arnd Sörensen , Valentina Lozza , Nuno Barros, Belina von Krosigk , Laura Neumann, Johannes Petzoldt , Axel Boeltzig , Felix Krüger and Kai Zuber. Outline. SNO+ = SNO + Liquid Scintillator ?

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The SNO+ Experiment: Overview and Status

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  1. The SNO+ Experiment: Overview and Status DPG Spring Meeting Dresden 2013 Arnd Sörensen, Valentina Lozza, Nuno Barros, Belina von Krosigk, Laura Neumann, Johannes Petzoldt, Axel Boeltzig, Felix Krüger and Kai Zuber

  2. Outline • SNO+ = SNO + Liquid Scintillator ? • Liquid Scintillator • From SNO to SNO+ • Phases of Operation • Neodymium loaded Phase (0νββ with 150Nd) • Pure Scintillator Phase • SNO+ @ TU Dresden • Summary & Outlook

  3. Location • @ SNOLab in Creighton Mine, Sudbury, Canada • deepest underground laboratory • 2 km ≈ 6000 meter water equivalent flat overburden • muon rate:

  4. Detector • acrylic vessel • 12 m diameter • 5 cm thickness • 780 t liquid scintillator (LAB) • ≈ 9100 PMTs in support structure (~ 54% coverage) • light-water shielding: • 1700 t inside • 5700 t outside • urylon liner and radon seal

  5. Linear Alkyl benzene (LAB) • fluor: 2 g/L PPO (= 2,5-Diphenyloxazol) • chemically compatible with acrylic • long scattering length & high optical transparency • high light yield (≈ 10,000 photons/MeV) • high purity available • inexpensive & safe LAB + PPO + (Nd)

  6. from SNO to SNO+ LAB lighter than water: SNO SNO+ rope hold up system + rope hold down system

  7. from SNO to SNO+

  8. from SNO to SNO+

  9. from SNO to SNO+

  10. Phases of Operation 2013 2014 - 2017/? 2017 - ?

  11. Neodymium loaded Phase

  12. Neodymium loaded Phase • 0.1% Nd loading • (43.7 kg 150Nd) • mee = 350 meV • 6.4% FWHM @3.37 MeV • IBM‐2 matrix element • 3 years running and • 50% fiducial Volume • (≈ 0.4 kt) • Borexino background levels + efficient tagging: • 214Bi: 99.9% reduction • 208Tl: 90.0% reduction • Background despite low Q-value through pile-up of e.g. 144Nd, 176Lu, 138La, 14C • 99% pile-up rejection while keeping 90% signal in ROI

  13. 0vββ with 150Nd Claim of Klapdor mee ≈ 170 – 530 meV [Nucl. Phys. B. (Proc. Supp.), S143:229, 2005] 0.1% Nd (6.4% FWHM @ 3.37 MeV) 0.3% Nd (9.0% FWHM @ 3.37 MeV) assuming Borexino background levels are reached and efficient tagging: • 214Bi: 99.9% reduction • 208Tl: 90.0% reduction

  14. Solar Phase Complete our understanding of the solar neutrino fluxes: • Super-K and SNO measured 8B neutrinos • Borexino measured 7Be and first probed pep neutrinos • pp was observed with Ga experiments • improve pep measurement • still missing CNO (probe for solar metallicity)

  15. pep Neutrinos • single energy: 1.442 MeV • very well predicted flux (≈ 2% uncertainty) • new physics models (NSI) predict different survival probabilities in vacuum matter transition regions [PLB 594, 347-354 (2004)] SNO, [arXiv:1109.0763]

  16. CNO Neutrinos new (low Z) old (high Z) [Peña-Garay & Serenelli, arXiv:0811.2424] • No direct observation of CNO neutrinos yet ! • probe for solar core metallicity • new solar physics developments suggest 30% lower metallicity

  17. Reactor Neutrinos no Oscillation 1186 events no Oscillation 308 events Flux is 5 times less than KamLAND BUT • SNO+ reactor spectrum, including oscillations, have sharp peaks and minima, that increase the parameter-fitting sensitivity for Δm12 Oscillation 176 events Oscillation 710 events

  18. Geo Neutrinos • Signal: • from β-decays in Earth’s mantle and continental crust (238U,232Th,40K) • local region extremely well studied due to mining • low reactor-v background in SNO+: Reactor/Geo ≈ 1.1 • check Earth heat production models / chemical composition (multi-site measurement in combination with Borexino, KamLAND)

  19. SNO+ @ TU Dresden

  20. Summary • SNO+ succeeds the SNO experiment by replacing heavy water with liquid scintillator • LS has higher light yield and lower threshold allows to investigate lower energy range ( E < 3.5 MeV ) • two phases planned: • Nd loaded phase to search for 0vββ decay of 150Nd • pure scintillator phase to observe pep and CNO solar neutrinos • reactor neutrino oscillation confirmation, geo neutrino investigation at geologically-interesting site, supernova neutrino watch … • SNO+ will be filled with water this year • 0vββ search starts next year

  21. Thank you for your attention !

  22. more

  23. pep, CNO Neutrinos - background • radio purity: • 14C is not a problem  pep signal is at higher energy • U, Th not a problem if one can repeat KamLAND scintillator purity • 40K, 210Bi (Radon daughter) • 85Kr, 210Po not a problem  pep signal is at higher energy SNO+ Borexino CNO pep CNO 11C pep 11C

  24. Solar Phase p-p solar fusion chain CNO cycle

  25. Sensitivity Goals

  26. pep sensitivity as a function of run time Assuming Borexino-level backgrounds are reached

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