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

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

Detector acrylic vessel 780 t liquid scintillator (LAB) 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

Linear Alkyl benzene (LAB) LAB + PPO + (Nd) 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

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

from SNO to SNO+ General rope-net hold down system new calibration (source manipulation) system scintillator purification plant

from SNO to SNO+ Electronics DAQ boards refurbished improved data flow replace & repair broken PMTs PMTs remapped

from SNO to SNO+ Calibration new low energy sources optical calibration via fibre-injected lasers and LEDs variety of gamma, alpha, beta and neutron sources

(neutrinoless-) double beta decay Phases of Operation detector commissioning water phase 150Nd loaded into liquid scintillator reactor-, geo- and supernova- neutrinos (neutrinoless-) double beta decay search for solar neutrinos: pep and CNO pure scintillator 2013 2014 - 2017/? short pure scintillator phase 2017 - ?

Neodymium loaded Phase large isotope mass, low background poor energy resolution neutrinoless 0vββ search with liquid scintillator 150Nd high Q-value: 3.371 MeV  low background fastest calculated decay rate complementary to other 0vββ experiments (76Ge, 136Xe …) in SNO+ LS successfully loaded with Neodymium 0.1% loading optimisation: 0.3% loading

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 Plot: Borexino Backgrounds + Nd Backgrounds + tagging Pile-Up: usually Nd2v + 144Nd … 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

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

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)

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 SNO, [arXiv:1109.0763] [PLB 594, 347-354 (2004)]

CNO Neutrinos old (high Z) new (low Z) [Peña-Garay & Serenelli, arXiv:0811.2424] photospheric absorbtion lines/abundances S-Factors 3D hydrodynamic models of near surface convection No direct observation of CNO neutrinos yet ! probe for solar core metallicity new solar physics developments suggest 30% lower metallicity

Reactor Neutrinos BUT Flux is 5 times less than KamLAND no Oscillation 308 events no Oscillation 1186 events Oscillation 176 events Oscillation 710 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

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) Multi Site measurement disentangle crust and mantle component

SNO+ @ TU Dresden 0vββ Phase pure scintillator phase design, development and test of 48Sc calibration source (3.33 MeV - ROI)  T 103.8 – Axel Boeltzig study of cosmogenic (n,p)- activation of Nd and LAB first measurement of natNd(p,x) cross sections [PRC 85, 014602 (2012)] study of underground- and thermal- neutron activation of Nd pure scintillator phase sensitivity study to solar neutrinos and neutrino oscillation parameters design, development and test of 57Co low energy (122 keV) calibration source to test the detector threshold and the low energy response alpha and proton quenching factor measurements [arXiv:1301.6403] cosmogenic muons and muon induced background tagging investigation of the 14C background

SNO+ will be filled with water this year 0vββ search starts next year 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

Thank you for your attention !

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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 Factor ~100 less muons from Borexino to SNO+ pep possible right away due to depth and size CNO possible if 11C tagging effective SNO+: 0.4kton (50% fid. volume) 1y exposure 5% E resolution Borexino: 100t CNO pep CNO 11C 11C pep

Solar Phase p-p solar fusion chain CNO cycle

Assuming Borexino-level backgrounds are reached Sensitivity Goals (stat) 1 year 2 years pep 9.1% 6.5% 8B 7.5% 5.4% 7Be 4% 2.8% pp A few %? CNO ~ 15%? Assuming Borexino-level backgrounds are reached

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