supported by: dpg spring meeting dresden 2013 arnd sörensen, valentina lozza, nuno barros, belina...
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supported by:
The SNO+ Experiment: Overview and StatusDPG Spring Meeting Dresden 2013
Arnd Sörensen, Valentina Lozza, Nuno Barros, Belina von Krosigk, Laura Neumann, Johannes Petzoldt, Axel Boeltzig, Felix Krüger and Kai Zuber
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Outline
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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
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Location
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@ SNOLab in Creighton Mine,
Sudbury, Canada deepest underground laboratory
2 km ≈ 6000 meter water
equivalent flat overburden
muon rate:
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Detector
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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
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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
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LAB + PPO + (Nd)
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from SNO to SNO+
SNO SNO+
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LAB lighter than water:
rope hold up system + rope hold down system
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from SNO to SNO+
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General
• rope-net hold down system• new calibration (source
manipulation) system• scintillator purification plant
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from SNO to SNO+
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Electronics
• DAQ boards refurbished• improved data flow• replace & repair broken
PMTs• PMTs remapped
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from SNO to SNO+
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Calibration
• new low energy sources• optical calibration via fibre-
injected lasers and LEDs• variety of gamma, alpha,
beta and neutron sources
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Phases of Operation
• detector commissioningwater phase
• 150Nd loaded into liquid scintillator
• reactor-, geo- and supernova- neutrinos
(neutrinoless-) double beta
decay
• search for solar neutrinos: pep and CNO
• reactor-, geo- and supernova- neutrinos
pure scintillator
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2013
2014 - 2017/?
2017 - ?
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Neodymium loaded Phase
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• 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
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Neodymium loaded Phase
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• 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
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0vββ with 150Nd
assuming Borexino background levels are reached and efficient tagging: 214Bi: 99.9% reduction 208Tl: 90.0% reduction
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[Nucl. Phys. B. (Proc. Supp.), S143:229, 2005]Claim of Klapdor mee ≈ 170 – 530 meV
0.3% Nd (9.0% FWHM @ 3.37 MeV)0.1% Nd (6.4% FWHM @ 3.37 MeV)
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Solar Phase
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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)
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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
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[PLB 594, 347-354 (2004)] SNO, [arXiv:1109.0763]
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CNO Neutrinos
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[Pena-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
old (high Z) new (low Z)
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Reactor Neutrinos
Flux is 5 times less than KamLANDBUT
SNO+ reactor spectrum, including oscillations, have sharp peaks and minima, that increase the parameter-fitting sensitivity for Δm12
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no Oscillation 308 events
no Oscillation 1186 events
Oscillation 176 events
Oscillation 710 events
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Geo Neutrinos
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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)
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SNO+ @ TU Dresden
0vββ 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
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Summary
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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
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Thank you for your attention !
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more
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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
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SNO+ Borexino
pep11C
CNOCNO 11C
pep
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Solar Phase
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p-p solar fusion chain
CNO cycle
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(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
Sensitivity Goals
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pep sensitivity as a function of run time
Assuming Borexino-level
backgrounds are reached