1. No s is good s Sheffield Physoc 21/04/2005 Jeanne Wilson A historical introduction to neutrinoless double beta decay

2. Introducing the Neutrino A* A e-e- The Beta Decay Puzzle Breaks energy and momentum conservation

3. Wolfgang Pauli, 1930 A* A e-e- C

4. Discovery Looking for something: very light, possibly massless electrically neutral produced alongside electron. very weakly interacting It would take 10 19 m (300 light years) of water to absorb a single neutrino. 25 years later Frederick Reines and Clyde Cowan

5. Project Poltergeist np e-e- e pn e+e+ e

6. Solar Neutrinos

7. 380,000 bottles of cleaning fluid Inverse Beta Decay Cl + e  Ar + e - Extract and measure the amount of argon converted in one month. expect 10 atoms in 10 30 !

8. Some of our neutrinos are missing

9. Neutrino Oscillations

10. –Mass difference  m 2 –Neutrino energy E –Distance travelled L –Mixing angle  Neutrino Oscillations

11. Sudbury Neutrino Observatory 1700 tonnes Inner Shielding H 2 O 1000 tonnes D 2 O 5300 tonnes Outer Shield H 2 O 12m Diameter Acrylic Vessel Support Structure for 9500 PMTs, 60% coverage Urylon Liner and Radon Seal

12. Reactions in SNO NCNC xx    npd C epd  e p -

13. How to Observe Neutrinos

14. Working in a Mine

15. Going Underground

16. Construction

17. Going Underground

18. Water Purity

19. Class 2000 Clean Room

20. Detector Operation

21. How to Observe Neutrinos Deep Underground Low Radioactive Backgrounds Precise Measurements Detailed Calibrations

22. Reactions in SNO NCNC xx    npd C epd  e p -

23. SNO Results 1.0 (  23%) 0.85 (  9%) 0.29 (  6%) CCNC Standard Solar Model Prediction = 0.34  0.04 CC NC Neutrino flux http://arxiv.org nucl-ex/0502021

24. Neutrino Masses Relative Mass Scale Mass Absolute Mass Scale

25. Neutrino Nature Majorana particle neutrino = antineutrino Dirac Particles Like all other fundamental particles Particle  antiparticle

26. Double Beta Decay np e-e- e np e-e- e 0+0+ 1+1+ 0+0+ (A,Z) (A,Z+1) (A,Z+2) Only 35 isotopes known in nature First proposed 1935 Maria Goeppet-Mayer 1935 First observed 1987

27. Neutrinoless Double Beta Decay np e-e- np e-e- e e e e X Neutrino  Antineutrino Only for Majorana neutrinos Gold-Plated Channel

28. How to detect double beta decay

29. Choose your isotope: Detector technology High isotopic abundance High energy release –Fast rate –Above U and Th background

30. Measuring neutrino mass  0  G 0 |M 0 | 2 m 2    ( b  E/Mt live ) 1/4 Phase space factor Nuclear Matrix element Background Energy resolution Mass of isotope Measuring time

31. The Ideal Experiment    ( b  E/Mt live ) 1/4 Large Mass (~ 1 ton) Radiopurity Demonstrated Technology Easy operation Large E release High Natural Abundance Small Volume: source = detector Good Energy Resolution Background separation

32. The COBRA experiment Cadmium-Telluride O-neutrino double-Beta Research Apparatus Use a large amount of CdTe (CdZnTe) Semiconductor Detectors Array of 1cm 3 CdTe detectors K. Zuber, Phys. Lett. B 519,1 (2001)

33. Semiconductors Insulator Semiconductor Metal Conduction band Valence band Energy gap ~6 eV~1 eV Free electrons holes Ionising particle creates electron-hole pairs Apply electric field – collect electrons and holes Amount of charge carriers  energy deposited

34. Isotopes in CdZnTe nat. ab. (%) Q (keV)Decay mode

35. The Ideal Experiment? Large Mass (~ 1 ton) Radiopurity Demonstrated Technology Easy operation Large E release High Natural Abundance Small Volume: source = detector Good Energy Resolution Background separation

36. Background Separation 0  

37. The COBRA Setup

38. The Crystals

39. Shielding

40. Electronics readout

41. Calibration 60 Co  1332 keV 60 Co  1173 keV 137 Cs  662 keV

42. The next step

43. Ssssummary 1931 – Neutrino first hypothesised 1956 – Neutrino first detected 2001 – Neutrino mass confirmed Today... Plans to search for 0  Decays T 1/2 ~ 10 25 years

44. Introducing me