1. Status of  decay Ruben Saakyan UCL

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

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

4. Neutrino MASS What do we want to know? Relative mass scale ( -osc) Mass hierarchy ( -osc and  ) Absolute mass scale (    cosmology ) Dirac or Majorana 1  3 e U e1 2 U e2 2 U e3 2 Mixing Only from  From -osc m min ~ 0 - 0.01 eV m min ~ 0.03 - 0.06 eV preferred by theorists (see-saw)

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

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

7.  Decay Basics. Energy Spectrum Q  Endpoint Energy 76 Ge example

8.  Decay Basics. Rates G – phase space, exactly calculable; G 0 ~ Q  5, G 2 ~ Q  11 M – nuclear matrix element. Hard to calculate. Uncertainties factor of 2-10 (depending on isotope) Must investigate several different isotopes! is effective Majorana neutrino mass Isotopes of Interest 48 Ca, 76 Ge, 100 Mo, 150 Nd, 136 Xe, 116 Cd, 96 Zr, 82 Se, 130 Te

9. Effective Majorana Mass U e1 2 m 1 U e2 2 m 2 U e3 2 m 3 min

10. Physics Reach Normal HierarchyInverted HierarchyDegenerate m 1 ~ 0 meV~55 meVM ≥ 100 meV m 2 ~ 7 meV~55 meVM m 3 ~ 55 meV~0 meVM ~ 5 meV28 or 55 meVM/2 or M Solar + KamLAND + Atmospheric (U e3 ~ 0)

11. The Experimental Problem ( Maximize Rate/Minimize Background) Natural Activity:  ( 238 U, 232 Th) ~ 10 10 years Target:  (0  ) > 10 25 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  (0 )  Slow  (2 ) rate  Identify daughter  Event reconstruction  Nuclear theory  All requirements can NOT be satisfied  Red – must be satisfied

13. Results from previous experiments < 0.35 – 1.0 eV m scale ~ 0.01 – 0.05 eV from oscillation experiments

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

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

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

17. CUORICINO Status T 1/2 (0 ) > 5×10 23 yr (90%) < 0.8 – 3.2 eV NEMO-3 < 0.9 – 2.1 eV (Preliminary - TAUP’03, September, Seattle ) 2.26 kg×yr (since Feb’03) BG  0.2 c/keV/kg/yr

18. A Great Number of Proposals ( Some may start taking data in 2008-2010) COBRATe-130,Cd-11610 kg CdTe semiconductors DCBANd-15020 kg Nd layers between tracking chambers SuperNEMOSe-82, Various100 kg of Se-82(or other) foil CAMEOCd-1161 t CdWO 4 crystals CANDLESCa-48Several tons CaF 2 crystals in liquid scint. CUORETe-130750 kg TeO 2 bolometers EXOXe-1361 ton Xe TPC (gas or liquid) GEMGe-761 ton Ge diodes in liquid nitrogen GENIUSGe-761 ton Ge diodes in liquid nitrogen GSOGd-1602 t Gd 2 SiO 5 :Ce crystal scint. in liquid scint. MajoranaGe-76500 kg Ge diodes MOONMo-100Mo sheets between plastic scint., or liq. scint. XeXe-1361.56 t of Xe in liq. Scint. XMASSXe-13610 t of liquid Xe

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

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

21. CUORE CUORICINO×20  270 kg 130 Te (~ 750 kg nat Te) Compact: 70×70×70 cm 3 5 yr in Gran Sasso: ~ 0.04 eV

22. The Majorana Project 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. Co-Spokespersons Frank Avignone Harry Miley

23. Majorana 0.5 ton of 86% enriched 76 Ge 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 ~ 0.03 eV

24. GErmanium NItrogen Underground Setup - GENIUS 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. Spokesperson Hans Klapdor-Kleingrothaus MPI GENIUS

25. 1 ton, ~86% enriched 76 Ge Naked Ge crystals in LN Very little material near Ge. 1.4x10 6 liters LN 40 kg test facility is approved. 100% efficient 5 yr in Gran Sasso: ~ 0.02 eV

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

27. EXO 10 ton, ~70% enriched 136 Xe 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 enr Xe prototype (no Ba ID) Isotope in hand 5 yr in a US underground lab ~ 0.05 eV

28. Future  projects sensitivity (5 yr exposure) ExperimentSource and Mass Sensitivity to T 1/2 (y) Sensitivity to (eV) * Majorana GENIUS 76 Ge, 500kg 76 Ge. 1000kg 3×10 27 5×10 27 0.03 – 0.07 0.02 – 0.05 CUORE 130 Te, 750kg(nat) 2×10 26 0.04 – 0.17 EXO 136 Xe 1 ton 8×10 26 0.05 – 0.12 SuperNEMO 82 Se (or other) 100 kg 2×10 26 0.04 – 0.11 * 5 different latest NME calculations

29. Summary Great progress over past decade: < 0.3-1 eV Oscillation expts: at least one neutrino  0.05 eV Next generation  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  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 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  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. Mod. Phys. Lett. A16, 2409 (2001)