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No s is good s

No s is good s. Sheffield Physoc 21/04/2005 Jeanne Wilson. A historical introduction to neutrinoless double beta decay. Introducing the Neutrino. The Beta Decay Puzzle Breaks energy and momentum conservation. A. A*. e -. A. C. A*. e -. Wolfgang Pauli, 1930. Discovery.

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No s is good s

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  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 The Beta Decay Puzzle Breaks energy and momentum conservation A A* e-

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

  4. Discovery Looking for something: • very light, possibly massless • electrically neutral • produced alongside electron. • very weakly interacting It would take 1019 m (300 light years) of water to absorb a single neutrino. 25 years later • Frederick Reines and Clyde Cowan

  5. Project Poltergeist e- n p e e+ e p n

  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 1030!

  8. Some of our neutrinos are missing

  9. Neutrino Oscillations

  10. Neutrino Oscillations • Mass difference m2 • Neutrino energy E • Distance travelled L • Mixing angle 

  11. Sudbury Neutrino Observatory 1000 tonnes D2O 12m Diameter Acrylic Vessel Support Structure for 9500 PMTs, 60% coverage 1700 tonnes Inner Shielding H2O 5300 tonnes Outer Shield H2O Urylon Liner and Radon Seal

  12. Reactions in SNO p -      d p e CC e       d p n NC x x

  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 p -      d p e CC e       d p n NC x x

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

  24. Neutrino Masses Absolute Mass Scale Mass Relative Mass Scale

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

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

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

  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G0|M0|2m2 Phase space factor Nuclear Matrix element <m>    ( bE/Mtlive)1/4 Background Measuring time Energy resolution Mass of isotope

  31. The Ideal Experiment <m>    ( bE/Mtlive)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 experimentCadmium-TellurideO-neutrino double-BetaResearchApparatus Use a large amount of CdTe (CdZnTe) Semiconductor Detectors Array of 1cm3 CdTe detectors K. Zuber, Phys. Lett. B 519,1 (2001)

  33. Semiconductors Insulator Semiconductor Metal Conduction band Free electrons Conduction band Energy gap ~6 eV ~1 eV Valence band Valence band 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 137Cs  662 keV 60Co  1173 keV 60Co  1332 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 T1/2 ~ 1025 years

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