SNO SNO+

Transcript SNO SNO+

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 150 Nd)  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 fibre injected lasers and LEDs • variety of gamma, alpha, beta and neutron sources 9

2013

water phase

• detector commissioning

2014 2017/?

(neutrinoless-) double beta decay

• 150 Nd loaded into liquid scintillator • reactor-, geo- and supernova- neutrinos

2017 ?

pure scintillator

• search for solar neutrinos: pep and CNO • reactor-, geo- and supernova- neutrinos 10

neutrinoless 0vββ search with liquid scintillator • large isotope mass, low background • poor energy resolution 150

Nd

• high Q-value: 3.371 MeV  low background • fastest calculated decay rate • complementary to other 0vββ experiments ( 76 Ge, 136 Xe …)

in SNO+

• LS successfully loaded with Neodymium • 0.1% loading • optimisation: 0.3% loading 11

• • • • • • • 0.1% Nd loading  (43.7 kg 150 Nd) m ee = 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:  214 Bi: 99.9% reduction  208 Tl: 90.0% reduction Background despite low Q-value through pile-up of e.g. 144 Nd, 176 Lu, 138 La, 14 C  99% pile-up rejection while keeping 90% signal in ROI 12

Claim of

Klapdor

m ee ≈ 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:  214 Bi: 99.9% reduction  208 Tl: 90.0% reduction 13

Complete our understanding of the solar neutrino fluxes:    Super-K and SNO measured 8 B neutrinos Borexino measured 7 Be 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 Oscillation 176 events no Oscillation 1186 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 Δm 12 17

Signal: n

+ +

from β-decays in Earth’s mantle and continental crust ( 238 U, 232 Th, 40 K)   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 48 Sc calibration source (3.33 MeV - ROI)  T 103.8 – Axel Boeltzig • study of cosmogenic (n,p)- activation of Nd and LAB • first measurement of nat Nd(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 57 Co low energy (122 keV) calibration source • to test the detector threshold and the low energy response • alpha and proton quenching factor measurements • investigation of the 14 C background [arXiv:1301.6403] • cosmogenic muons and muon induced background tagging 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 150 Nd  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 !

 radio purity:  14 C is not a problem   U, Th not a problem

purity pep signal is at higher energy one can repeat KamLAND scintillator   40 K, 210 Bi (Radon daughter) 85 Kr, 210 Po not a problem  pep signal is at higher energy SNO +

Counts per 0.1 ktons per 1.0 years per 5 keV

Borexino CNO pep 11 C CNO pep 11 C 23

p-p solar fusion chain CNO cycle 24

(stat) pep

B

Be pp CNO 1 year 9.1% 7.5% 4% 2 years A few %?

~ 15%?

6.5% 5.4% 2.8%

Assuming Borexino-level backgrounds are reached