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Double Beta Decay in SNO +. Huaizhang Deng University of Pennsylvania. Collaboration. Brookhaven National Laboratory: R. Hahn, M. Yeh, Y. Williamson, A. Garnov Carleton University: K. Graham Idaho State University: K. Keeter, J. Popp, E. Tatar

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Double Beta Decay in SNO +

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Double beta decay in sno

Double Beta Decay in SNO+

Huaizhang Deng

University of Pennsylvania



  • Brookhaven National Laboratory: R. Hahn, M. Yeh, Y. Williamson, A. Garnov

  • Carleton University: K. Graham

  • Idaho State University: K. Keeter, J. Popp, E. Tatar

  • Laurentian University: D. Hallman, C. Virtue, A. Labelle

  • LIP Lisbon: S. Andringa, N. Barros, J. Maneira

  • Queen's University:

    • M. Boulay, M. Chen, X. Dai, E. Guillian, P. Harvey, C. Kraus, C. Lan,

      A. McDonald, S. Quirk, P. Skensved, V. Novikov, A. Wright, A. Chia,

      M. Gobien, J. Lau


    • B. Cleveland, F. Duncan, R. Ford, N. Gagnon, J. Heise, C. Jillings,

    • I. Lawson

  • Technical University of Munich: F. v. Feilitzsch, L. Oberauer

  • University of Alberta: A. Hallin, C. Krauss

  • University of Pennsylvania:

    • G. Beier, H. Deng, B. Heintzelman, J. Secrest, T. Shokair

  • University of Sussex: K. Zuber

  • University of Texas at Austin: J. Klein



  • 150Nd double beta decay

  • The SNO+ detector

  • 150Nd loaded scintillator in SNO+ detector

  • The sensitivity of SNO+ to m

  • Comparison with other experiments

  • Conclusions

Double beta decay

Double Beta Decay

Neutrinos are Majorana particles

(Z, N)

(Z+2, N-2)

Neutrinos have masses


48Ca, 76Ge, 82Se, 100Mo, 130Te

136Xe, 150Nd …

Neodymium 150 nd

Neodymium - 150Nd


150Nd 150Sm + 2e + 2

 = 2.9x1019 year


150Nd 150Sm + 2e

Q = 3.37 MeV

 = ? year



F. Avignone, Nucl. Phys. B (proc. Suppl) 143 (2005) m=40 meV

V.A. Rodin et al., Nucl. Phys. A 766, 107 (2006) m=50 meV

Double beta decay in sno

Sudbury Neutrinoless Observatory (SNO+)

Sudbury Neutrino Observatory (SNO)

  • 2092 meters deep underground

  • 1000 tons of ultrapure D2O

  • in a 12 meter diameter

  • acrylic vessel

  • 1000 tons of ultrapure liquid

  • scintillator in a 12 meter

  • diameter acrylic vessel

Already Exists !

  • 7000 tons of ultrapure H2O

  • as shield

  • 9500 PMTs mounted on a

  • 18 meter diameter frame

  • electronics, DAQ,

  • understanding of our detector




Scintillator in sno

Scintillator in SNO+

  • compatible with acrylic, undiluted

  • high light yield (because it’s undiluted)

  • Pure, light attenuation length in excess of 20 m at 420 nm

  • high flash point (130°C) safe

  • low toxicity safe

  • low cost (relative to other organic solvents)

  • smallest scattering of all scintillating solvents investigated

  • Petresa Canada plant in Quebec makes 120 kton/year, $1600 per ton delivered.

Lab and fluor

LAB and Fluor

  • works fine with standard fluors

    • PPO, butyl-PBD, PPD

    • 2 g/L concentration works fine

LAB-PPO energy transfer efficiency

Method 1 (fluorescence emission method): measure the fluorescence excitation and emission of PPO-LAB solution; excitation at 318nm (LAB excitation), integrate emission range from 320 to 550nm (PPO emission)Method 2 (decay time method): excitation at 250nm, emission 360nm, measure the decay times of PPO-LAB solution, compare to the decay time of pure PPO

Light yield

Light Yield



preliminary measurement

Decay times of scintillations

Decay Times of Scintillations

Nd loaded lab

Nd Loaded LAB

Other studies

Other Studies

  • Acrylic vessel holding structure

  • Long time stability of Nd loaded LAB with acrylic

  • Optics of Nd loaded LAB

  • Upgrade of electronic system

  • Modification of software packages, Monte Carlo

Energy spectrum in sno

Energy Spectrum in SNO+

Extract number of 0 events

Extract Number of 0 Events

Discovery potential

Discovery Potential

3 sigma indication

five sigma discovery



Fabrice Piquemal, Lepton Photon 2007

Calculation with NME from Rodim et al., Suhonen et al., Caurier et al. PMN07



  • The 150Nd is a good candidate for 0 decay due to large Q and favorable nuclear matrix element

  • The Nd can be dissolved into SNO+ liquid scintillator with long term stability and good optics.

  • The large statistics compensate the relatively poor energy resolution in SNO+. The sensitivity to neutrino mass is comparable with other experiments

  • The SNO detector has been built. We could start SNO+ soon.

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