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
supported by:

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
2
 @ SNOLab in Creighton Mine,
Sudbury, Canada
 deepest underground laboratory
 2 km ≈ 6000 meter water
equivalent flat overburden
 muon rate:
3
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
4
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
5
LAB lighter than water:
SNO
SNO+
rope hold up system
+ rope hold down system
6
General
• rope-net hold down system
• new calibration (source
manipulation) system
• scintillator purification plant
7
Electronics
• DAQ boards refurbished
• improved data flow
• replace & repair broken
PMTs
• PMTs remapped
8
Calibration
• new low energy sources
• optical calibration via fibreinjected lasers and LEDs
• variety of gamma, alpha,
beta and neutron sources
9
2013
water phase
2014 2017/?
(neutrinoless-)
double beta
decay
2017 ?
pure scintillator
• detector commissioning
•
150Nd
loaded into liquid
scintillator
• reactor-, geo- and
supernova- neutrinos
• search for solar neutrinos:
pep and CNO
• reactor-, geo- and
supernova- neutrinos
10
neutrinoless 0vββ search • large isotope mass, low background
• poor energy resolution
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
11
• 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
12
Claim of Klapdor mee ≈ 170 – 530 meV
0.1% Nd (6.4% FWHM @ 3.37 MeV)
[Nucl. Phys. B. (Proc. Supp.), S143:229, 2005]
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
13
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)
14


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]
15
old (high Z)
new (low 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
16
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 parameterfitting sensitivity for Δm12
17
Signal:
n e + p ® e+ + n
n e 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)
18
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
19

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
20
Thank you for your attention !
21
more
22

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
Counts per 0.1 ktons per 1.0 years per 5 keV
pep
11C
pp
pep
be7
b8
cno
c11-decays
CNO
Analytically generated spectra with 5%/ E resolution
Borexino
104
103
102
11C
10
pep
1 1.2 1.4 1.6 1.8 2
visible energy [MeV]
CNO
1
10-1
0 0.2 0.4 0.6 0.8
SNO
+
23
p-p solar fusion chain
CNO cycle
24
(stat)
pep
8B
7Be
pp
CNO
1 year
2 years
9.1%
6.5%
7.5%
5.4%
4%
2.8%
A few %?
~ 15%?
Assuming Borexino-level backgrounds are reached
Assuming
Borexino-level
backgrounds are
reached