1. Double Beta Decay - status and future
Double beta decay basics
Experimental challenges
Current experimental status
HM(HKK) result
Future experimental programmes
Dark matter and bb0n
Based on talks at ApPEC Peer Review of bb0n, Nu2002 (heavily) ….and a night in the Lamb with Kai Züber and Roland

2. Double Beta Decay
Cremonesi Nu2002

3. bb0n Rates
Cremonesi Nu2002

4. Why do bb0n?
Cremonesi Nu2002

5. Experimental Considerations
Measure this
Cremonesi Nu2002

6. Key Issues Multi-isotopic targets Enrichment
“Redundancy, redundancy, redundancy” (J. Bahcall)
Background removal by different peak positions (ie noise peak at Q)
Enrichment
Radio-isotopic backgrounds
Energy Resolution
Discrimination
Removal of gamma, beta, neutron backgrounds
bb(2n) background irremovable (separate peaks)
Co-location of daughter ion
Theory
Matrix elements
Analysis techniques
Esp. in light of H-M claim

7. Current Experimental Limits
Cremonesi Nu2002

8. Current Experimental Limits
Cremonesi Nu2002

9. Heidelberg Moscow Experiment
Cremonesi Nu2002

10. HM(HVKK) Result
Cremonesi Nu2002

11. HM(HVKK) Result
Cremonesi Nu2002

12. Comments on HM(HVKK)
Cremonesi Nu2002

13. Reply to the comments on HM(HVKK)
Cremonesi Nu2002

14. IGEX: Canfranc
hep-ex

15. Thermal detectors - Milano DB
Cremonesi Nu2002

16. Milano DBD-II
Cremonesi Nu2002

17. MDBD-II: Results
Cremonesi Nu2002

18. MDBD-II: Background
Cremonesi Nu2002

19. Proposed Experiments
Cremonesi Nu2002

20. Proposed Experiments Half life normalised to 5 years operation
10’s kg scale
Tonne scale
Matrix element range. Half life for 50meV mass (in 1026y)
Elliott and Vogel Ann. Rev. Nucl. Part. Sci. 52 (2002)

21. Modularity and prototyping
Discrimination through segmentation
Increase in support materials
GENIUS vs. Majorana
Systematics checks
Prototyping
Direct scale-up of current technology won’t require prototyping - too expensive?
Prototype is first module
All experiments involved in prototyping
Handling scale up issues (cryostats, mass, etc)
Handling readout options (laser tag, WLS fibres)
Cross check against Monte Carlo

22. NEMO-III
Cremonesi Nu2002

23. NEMO-III
Cremonesi Nu2002

24. CUORE
Cremonesi Nu2002

25. CUORicino
Cremonesi Nu2002

26. EXO - Xenon
Cremonesi Nu2002

27. EXO - two approaches
Cremonesi Nu2002

28. Majorana
Cremonesi Nu2002

29. GENIUS
Cremonesi Nu2002

30. GENIUS-TF
Cremonesi Nu2002

31. GEM
Cremonesi Nu2002

32. DCBA/COBRA
Cremonesi Nu2002

33. Pros and Cons Technique Prototyping MultiIsotope Enrichment Resolution
Mass limit
Discrimination
Problems
CAMEO
CdWO4 scintillator
Use of B-CF 65kg array No
Needed
10%
1 tonne
Active shield
Enrichment costs
COBRA
CdTe
diodes
Underway
Yes
No (?)
<1%
10kg
Segmemtation
Neutron background
CUORE
TeO2 Bolometer
Cuoricino approved
Not needed
(34% natural)
0.2%
Segmentation
Materials close to target
EXO
LXe or Xe TPC
Approved
(Ba tag test, 100kg Lxe)
<2%
10 tonne
Co-location of daughter
PSD
Cost of enrichment
Ba ion extraction
GENIUS
Naked HPGe
Genius-TF approved
G-TF: natural
G: 86% enrichment
0.3%
Use of LN
Cosmogenics
Majorana
HPGe
1 Ge det under construction
Needed (8% -> 86%)
420kg
MOON
Mo & Scintillator
WLS/Scint/Mo testing 7%
3 tonne
(34 tonnes nat. Mo)
Localisation
High Q (3.03MeV)
NEMO
Tracking chamber Scintillator
NEMO-I/II
Tracking
Time of flight
Magnetic field
Radioisotopic impurity
Scale-up?
TGV
CaCO3 foils
TGV 1 (1g)
Required (73%)
? TGV-2: 10g
Enrichment from CaF2
Mass

34. bb0n and dark matter Many common elements for rare event searches
Theoretically prejudice for max sensitivity required
DM: 10-10pb covers most of SUSY models
bb: >10 meV from oscillations
Both require large mass targets (~1 tonne)
Low backgrounds required
High radio-purity materials
Good shielding
Discrimination required
DM: nuclear vs. electron recoil, spatial
bb: spatial (co-location of daughter)
Good resolution/threshold (high light yield, etc.)
DM: keV range - bite into DM spectrum
bb: MeV range - separate peaks at Q
Can we do both in one detector?
Xenon is an obvious candidate to consider within U.K.
Beware!

35. Xenon experience in UK/RAL
Gotthard Xe TPC DB experiment (Roland)
ZEPLIN dark matter programme
(RAL, IC, Shef)

36. ZEPLIN as bb0n experiment
Developing ideas for combining dark matter and bb0n experiments
Key issues are
Energy scales of interest
Primarily a DAQ issue, saturation of readouts, etc.
Discrimination of backgrounds
Can position sensitivity in ZEPLIN be improved to check co-locality in DB?
Resolution at MeV scales
Looks OK in second generation DM targets
There is also b+b+ capability
124Xe (0.1% in nat. Xe) is one of seven known b+b+ emitters
2nb+ b+ gives 4x 511keV photon signal
2nb+EC gives X-ray (30keV) and 2x 511keV photon signal (
2nECEC gives 2x X-ray (30keV) signal
Current limits for 124Xe are T0.52n > 2x1014 years, T0.50n > 4x1017 years

37. Conclusions The bb0n decay search has the promise of illuminating
Absolute mass scale of neutrinos
(note this is effective mass, unlike beta end point: KATRIN)
Lepton number violation
Majorana vs. Dirac description
Current limits/claims 300meV
H-M (HVKK) Claim contested
Oscillation results encourage meV searches
Several programmes suggested on Ge, Xe, Te, Mo
Need large scale, good resolution, discrimination, enrichment
Possibility of DM detectors as DB
ZEPLIN programme?
One man’s background….