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Double Beta Decay Experiments

Jeanne Wilson University of Sussex 29/06/05, RAL. Double Beta Decay Experiments. Contents. What is double beta decay and what can it tell us? Experimental requirements Experimental status A closer look at a selection of experiments. e -. n. p.  e.  e. n. p. e -. 1 +. (A,Z+1).

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Double Beta Decay Experiments

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  1. Jeanne Wilson University of Sussex 29/06/05, RAL Double Beta Decay Experiments

  2. Contents • What is double beta decay and what can it tell us? • Experimental requirements • Experimental status • A closer look at a selection of experiments

  3. e- n p e e n p e- 1+ (A,Z+1) 0+ (A,Z) 0+ (A,Z+2) Double Beta Decay (2) (A,Z)  (A,Z+2) + 2 e- + 2e Only 35 isotopesknown in nature

  4. Neutrinoless mode (0) e- n p L = 2 (A,Z)  (A,Z+2) + 2 e- e X e n p e-

  5. What Can We Learn? • Dirac or Majorana? • Absolute Mass Scale • Mass Hierarchy? 0=(T1/2)-1=G0|M0|2m2 Phase space factor Nuclear Matrix element

  6. Normal Inverted Degenerate m3 m2 m1 m2 m1 m3 0 Mass Hierarchy

  7. What Can We Learn? • Dirac or Majorana? • Absolute Mass Scale • Mass hierarchy? • CP violation? • Matter-Antimatter Asymmetry

  8. CP Violation? Atmospheric Solar If sin 13 0  CP-violation Majorana : U= UPMNS diag(1,e i1 ,e i2 )

  9. mee = Ue12m1 Ue22m2 Ue32m3 The Neutrino Mass relative CP phases = 1 me =  |Uek|2 mk

  10. Experimental Requirements

  11.  Decay Endpoint Energy

  12. Requirements for 0 Searches • High Q value • High Isotopic Abundance • Background Rejection • Ideally no background in signal region OR • Clear identification of decay

  13. 2 Decays • The ultimate, irreducible background 76Ge (Diode) 0.2% 130Te (Bolometer) 0.4% 136Xe (TPC) 3.3% CdZnTe (Semiconductor) 3-4% 100Mo, 82Se (Plastic scintillator) ~14% S. Elliott, P. Vogel, Ann. Rev. Nucl. Part. Sci. 2002

  14. Requirements for 0 Searches • High Q value • High Isotopic Abundance • Background Rejection • Good Energy Resolution • Theory 0=(T1/2)-1=G0|M0|2m2

  15. Nuclear Matrix Elements P. Vogel, PDG 02 A factor 3 uncertainty in the NME means a factor of ~10 in half-life.

  16. Requirements for 0 Searches • High Q value • High Isotopic Abundance • Background Rejection • Good Energy Resolution • Theory • possibility to measure 2 modes too • Large Isotope Sample

  17. 76Ge We Are Here Next Generation Our Dreams How Much Mass? ~ 1025 yrs ~ 1026 yrs ~ 1027 yrs ~ 1028 yrs ~ 1029 yrs

  18. How Much Mass? T1/2 = ln2 • a•NA• M • t / N (t<<T) ( Background free) 50 meV half-life measurements of 1026-27y 1 event/y you need 1026-27 source atoms ~ 1000 moles of isotope  ~100 kg

  19. Experiments

  20. HM Cuoricino NEMO3 Half Life (years) CdWO4 CaF2 Experimental Status Disclaimer : This is not a complete list of experiments!!! 90% C.L.

  21. Heidelberg-Moscow • 11kg 76Ge (86-88% enrichment) • 5 crystals • Aug 1990 – May 2003 (71.7 kgy) • 0.2% or better energy resolution 2001 – Evidence for 0 peak at 2039keV

  22. References Evidence H.V. Klapdor-Kleingrothaus et al., Mod. Phys. Lett. A 16,2409 (2001) Critical comments F. Feruglio et al., hep-ph/0201291 C.A. Aalseth et al., hep-ex/0202018 Reply H.V. Klapdor-Kleingrothaus, hep-ph/0205228 H.L. Harney, hep-ph/0205293 Latest Heidelberg-Moscow results H.V. Klapdor-Kleingrothaus et al., Phys. Lett. B586 (2004) 198-212

  23. Evidence? • Weak 214Bi lines 2010.7, 2016.7, 2021.8, 2052.9keV • 0 peak • ? Electron conversion of 2118keV  line2030keV • 2039keV peak has 4.2 significance <m> = 0.2-0.6 eV

  24. Improvements • More statistics – data taking till May 2003 • Stricter acceptance conditions 54.98 kgy  50.57 kgy • Refined summing procedure • Better E calibration of individual runs • Various fit methods • Simultaneous fit 2000-2060keV • Time structure of events – pulse shape for single site events

  25. New Germanium Experiments

  26. GERDA • GERmanium Detector Array • At LNGS, (Italy, Russia, Germany, Poland) • Germanium Diodes • Inherited from HM, IGEX • Cu cryostat filled with liquid N • 3m thick Čerenkov H2O shield

  27. GERDA Phase I • Nearly 20kg Ge (86% enrichment) • Crystal characterisation • Install in cryostat, summer 2006 • T1/2>1.2 1025 sensitivity in 1 year Phase II • New crystal material – working on purity and efficiency of crystal growing • Crystal segmentation • LAr in cryostat for background suppression • 100kg years  T1/2>2 1026 sensitivity

  28. Majorana • 500kg enriched Ge Segmented detectors • Based on IGEX technology • background reduced by >50 • cosmogenic n spallation • 10 years  T1/2>4 1027 years <m> ~ 0.03-0.04 eV

  29. Majorana • Design optimisation underway • DoE review process in progress • Start with 180kg experiment • Easily extendable to 500kg or 1 ton. • Collaboration with GERDA experiment for simulations. • Possibly combine for ton scale experiment

  30. Tellurium Experiments

  31. Tellurium Experiments MiBETA 6.8kg TeO2 Cuoricino 40.7 kg TeO2 CUORE ~ 750 kg TeO2 • Bolometers – E release in crystals gives measurable T increase at ~10mK (~1MeV/0.1mK) • Detector anticoincidence for bkg suppression

  32. Cuoricino and CUORE Cuoricino • 0.18 ± 0.01 bkg events/keV/kg/y • Resolution ~7.5 ±2.9 keV at 2615 keV • T1/2 > 1.8 .1024 years (10.85 kgy of data) • 5 years  9 .1024 years (<m> 0.1-0.7eV) CUORE • 19 Cuorocino-like towers • Goal 0.001-0.01 bkg events/keV/kg/y • Sensitivity <m> ~ 0.02-0.13eV

  33. NEMO

  34. NEMOIII • Running in Frejus UG lab since Feb 2003 • 10kg 0 isotopes in 20m2 cylinder • Passive sources • Event identification: • Drift wire tracking chamber • Plastic scintillator calorimeter • 25Gaus field

  35. NEMOIII First Results • 82Se (Q=2995keV) T1/2 > 1.5 1023 years <m> = 1.3-3.0 eV • 100Mo (Q=3034keV) T1/2 > 3.5 1023 years <m> = 0.65-1.0 eV (V-A), 90%CL • T1/2 (2) for 116Cd, 150Nd, 96Zr and 48Ca

  36. SuperNEMO • NEMOIII with 5 years Radon-free data: 6914 g of 100Mo T1/2> 4 .1024 y <m> < 0.2 – 0.35 eV 932 g of 82Se T1/2> 8 .1023 y <m> < 0.65 – 1.8 eV • SuperNEMO = NEMOIII*10 + better E/E • Sensitivity ~0.03 – 0.06 eV in 5 yr • Only background from 2 tail • Improve E/E from (14%-16%)/E to (7%-9%)/E • 100Mo, 82Se116Cd and 130Te

  37. EXO

  38. EXO • > 1 ton Liquid Xe TPC (90% enriched 136Xe) • Ionisation + Scintillation signals  Good energy resolution • Identification of 136Badaughter  Clear signal • Electrostatic probe • Laser fluorescence • Prototype late 2005 • 200kg at WIPP • No Ba identification

  39. COBRA

  40. COBRA • Large array of 1cm3 CdZnTe semiconductor crystals • Coincidences, pixellisation and pulse shape analysis • Good E resolution (~4%) • Room temperature • Multiple isotopes, 116Cd, 130Te, 106Cd

  41. ++ Modes p n e+ e+ n p Q-4mec2 • (A,Z)  (A,Z-2) + 2 e+ (+2e)++ Q-2mec2 • e- + (A,Z)  (A,Z-2) + e+ (+2e )+/EC Q • 2 e- + (A,Z)  (A,Z-2) (+2e)EC/EC Enhanced sensitivity to right handed weak currents (V+A) M. Hirsch et al., Z. Phys. A 347,151 (1994)

  42. COBRA • 0.4kg prototype (64 crystals) – Autumn 2005 • Prove background reduction and rejection • Fully funded (UK) • Physics: Access to 22EC 113Cd 2 T1/2 D.Dobbos

  43. Multipurpose Experiments • XMass : liquid 136Xe detector • Solar neutrinos and Dark matter • MOON : 100Mo scintillator detector • Real time studies of low E solar neutrinos • GENIUS : 76Ge in LN • Dark matter • + others

  44. Summary and Outlook • 0 is a gold plated channel to probethe fundamental character of neutrinos • Large mass >100kg - ton required for 0 discovery • A number of different approaches on the market

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