The SNO+ Experiment: Overview and Status

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

Outline

2

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

Location

3

@ SNOLab in Creighton Mine, Sudbury, Canada

deepest underground laboratory 2 km ≈ 6000 meter water

equivalent flat overburden

muon rate:

Detector

4

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

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

5

LAB + PPO + (Nd)

from SNO to SNO+

SNO SNO+

6

LAB lighter than water:

rope hold up system + rope hold down system

from SNO to SNO+

7

General• rope-net hold down system• new calibration (source

manipulation) system• scintillator purification plant

from SNO to SNO+

8

Electronics• DAQ boards refurbished• improved data flow• replace & repair broken

PMTs• PMTs remapped

from SNO to SNO+

9

Calibration

• new low energy sources• optical calibration via fibre-

injected lasers and LEDs• variety of gamma, alpha,

beta and neutron sources

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

10

2013

2014 - 2017/?

2017 - ?

Neodymium loaded Phase

11

• 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

12

• 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

0vββ with 150Nd

assuming Borexino background levels are reached and efficient tagging: 214Bi: 99.9% reduction 208Tl: 90.0% reduction

13

[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)

Solar Phase

14

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

15

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

CNO Neutrinos

16

[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)

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

17

no Oscillation 308 events

no Oscillation 1186 events

Oscillation 176 events

Oscillation 710 events

Geo Neutrinos

18

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)

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

19

Summary

20

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 !

21

more

22

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

23

SNO+ Borexino

pep11C

CNOCNO 11C

pep

Solar Phase

24

p-p solar fusion chain

CNO cycle

(stat) 1 year 2 yearspep 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

pep sensitivity as a function of run time

Assuming Borexino-level

backgrounds are reached