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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

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

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


preliminary measurement

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

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.