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Status of bb decay

Status of bb decay. Ruben Saakyan UCL. Outline. Motivation bb decay basics Results so far Current experiments Future projects and sensitivity. Motivation. Neutrino Mixing Observed !. From KamLAND, solar n and atmospheric n. VERY approximately.

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Status of bb decay

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  1. Status of bb decay Ruben Saakyan UCL

  2. Outline • Motivation • bb decay basics • Results so far • Current experiments • Future projects and sensitivity

  3. Motivation Neutrino Mixing Observed ! From KamLAND, solar n and atmospheric n VERY approximately

  4. Neutrino MASSWhat do we want to know? • Relative mass scale (n-osc) • Mass hierarchy (n-osc and bb) • Absolute mass scale • (bb +3H b + cosmology) mmin~ 0 - 0.01 eV mmin~ 0.03 - 0.06 eV Dirac or Majorana preferred by theorists (see-saw) ne n1 n2 n3 Ue12 Ue22 Ue32 Mixing Only from bb From n-osc

  5. bb Decay Basics Qbb Endpoint Energy In many even-even nuclei, b decay is energetically forbidden. This leaves bb as the allowed decay mode.

  6. bb Decay Basics 2nbb and 0nbb DL = 2 • 2nbb – Allowed in SM second order weak process. Observed for • several isotopes • 0nbb – Requires massive Majorana neutrinos (even in presence of • alternative mechanisms)

  7. bb Decay Basics. Energy Spectrum 76Ge example Qbb Endpoint Energy

  8. bb Decay Basics. Rates G – phase space, exactly calculable; G0n ~ Qbb5, G2n ~ Qbb11 M – nuclear matrix element. Hard to calculate. Uncertainties factor of 2-10 (depending on isotope) Must investigate several different isotopes! <mn> is effective Majorana neutrino mass Isotopes of Interest 48Ca, 76Ge, 100Mo, 150Nd,136Xe, 116Cd, 96Zr, 82Se,130Te

  9. Effective Majorana Mass Ue22 m2 <mee> Ue32 m3 min Ue12 m1

  10. Physics Reach Solar + KamLAND + Atmospheric (Ue3~ 0)

  11. The Experimental Problem( Maximize Rate/Minimize Background) Natural Activity: t(238U, 232Th) ~ 1010 years Target: t(0nbb) > 1025 years  Detector Shielding Cryostat, or other experimental support Front End Electronics etc. + Cosmic ray induced activity

  12. An Ideal Experiment • Large Mass (0.1t) • Good source radiopurity • Demonstrated technology • Natural isotope • Small volume, source = detector • Tracking capabilities • Good energy resolution or/and Particle ID • Ease of operation • Large Q value, fast bb(0n) • Slow bb(2n) rate • Identify daughter • Event reconstruction • Nuclear theory • All requirements can NOT be satisfied • Red – must be satisfied

  13. Results from previous experiments <mn> < 0.35 – 1.0 eV mscale~ 0.01 – 0.05 eV from oscillation experiments

  14. Hieldeberg-Moscow (Gran Sasso)(Spokesperson: E. Klapdor-Kleingrothaus, MPI) <mn> = 0.4 eV ??? • 5 HPGe 11 kg, 86% 76Ge • DE/E 0.2% • >10 yr of data taking <mn> < 0.3 – 0.7 eV If combine HM and IGEX

  15. Current Experiments CUORICINO (bolometer) NEMO-3 (Tracking calorimeter) See Jenny’s talk

  16. CUORICINO Detector (Gran Sasso)(Milano LNGS, Firenze, Berkeley, S. Carolina) ~ 14 kg 130Te • High natural abundance • of 130Te – 34% (no enrichment) • Good DE/E ~0.3% at 2.529 MeV Spokesperson: E. Fiorini, Milano

  17. CUORICINO Status • 2.26 kg×yr (since Feb’03) • BG  0.2 c/keV/kg/yr T1/2(0n) > 5×1023 yr (90%) <mn> < 0.8 – 3.2 eV NEMO-3 <mn> < 0.9 – 2.1 eV (Preliminary - TAUP’03, September, Seattle )

  18. A Great Number of Proposals(Some may start taking data in 2008-2010)

  19. COBRA, SuperNEMO See later talks by Kai Zuber, Ruben Saakyan

  20. Cryogenic Underground Observatory for Rare Events - CUORE Spokesperson Ettore Fiorini Milano Berkeley Firenze Gran Sasso Insubria (COMO) Leiden Milano Neuchatel U. of South Carolina Zaragoza

  21. CUORE CUORICINO×20  270 kg 130Te (~ 750 kg natTe) Compact: 70×70×70 cm3 5 yr in Gran Sasso: <mn> ~ 0.04 eV

  22. The Majorana Project Co-Spokespersons Frank Avignone Harry Miley Duke U. North Carolina State U. TUNL Argonne Nat. Lab. JINR, Dubna ITEP, Moscow New Mexico State U. Pacific Northwest Nat. Lab. U. of Washington LANL LLNL U. of South Carolina Brown Univ. of Chicago RCNP, Osaka Univ. Univ. of Tenn.

  23. Majorana • 0.5 ton of 86% enriched 76Ge • Very well known and successful technology • Segmented detectors using pulse shape discrimination to improve background rejection. • Prototype ready to go this autumn/winter. (14 crystals, 1 enriched) • 100% efficient • Can do excited state decay. 5 yr in a US undegr lab <mn> ~ 0.03 eV

  24. GErmanium NItrogen Underground Setup - GENIUS Spokesperson Hans Klapdor-Kleingrothaus MPI MPI, Heidelberg Kurchatov Inst., Moscow Inst. Of Radiophysical Research, Nishnij Novgorod Braunschweig und Technische Universität, Braunschweig U. of L'Aquila, Italy Int. Center for Theor. Physics, Trieste JINR, Dubna Northeastern U., Boston U. of Maryland, USA University of Valencia, Spain Texas A & M U. GENIUS

  25. GENIUS • 1 ton, ~86% enriched 76Ge • Naked Ge crystals in LN • Very little material near Ge. • 1.4x106 liters LN • 40 kg test facility is approved. • 100% efficient 5 yr in Gran Sasso: <mn> ~ 0.02 eV

  26. Enriched Xenon Observatory - EXO Spokesperson Giorgio Gratta Stanford U. of Alabama Caltech IBM Almaden ITEP Moscow U. of Neuchatel INFN Padova SLAC Stanford U. U. of Torino U. of Trieste WIPP Carlsbad

  27. EXO • 10 ton, ~70% enriched 136Xe • 70% effic., ~10 atm gas TPC or LXe chamber • Optical identification of Ba ion. • Drift ion in gas to laser path or extract on cold probe to trap. • 100-200-kg enrXe prototype (no Ba ID) • Isotope in hand • 5 yr in a US underground lab <mn> ~ 0.05 eV

  28. Future bb projects sensitivity(5 yr exposure) * 5 different latest NME calculations

  29. Summary • Great progress over past decade: <mn> < 0.3-1 eV • Oscillation expts: at least one neutrino  0.05 eV • Next generation bb experiments will reach 0.03 – 0.1 eV (good if inverted hierarchy) • Start in ~2008 • The next after next generation will address  0.01 eV • Nuclear theory input needed • Exciting time for bb decay

  30. Things to read… S.R. Elliott, P. Vogel, Annu. Rev. Nucl. Part. Sci. 52(2002) hep-ph/0202264

  31. BACKUP SLIDES

  32. The Controversy. Locations of claimed peaks Mod. Phys. Lett. A16, 2409 (2001) If one had to summarize the controversy in a short statement: Consider two extreme background models: 1. Entirely flat in 2000-2080 keV region. 2. Many peaks in larger region, only bb peak in small region. These 2 extremes give very different significances for peak at 2039 keV. KDHK chose Model 2 but did not consider a systematic uncertainty associated with that choice.

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