Double Beta Decay - status and future

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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
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Double Beta Decay
Cremonesi Nu2002
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bb0n Rates
Cremonesi Nu2002
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Why do bb0n?
Cremonesi Nu2002
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Experimental Considerations
Measure this
Cremonesi Nu2002
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Key Issues

• Multi-isotopic targets
• 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

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Current Experimental Limits
Cremonesi Nu2002
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Current Experimental Limits
Cremonesi Nu2002
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Heidelberg Moscow Experiment
Cremonesi Nu2002
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HM(HVKK) Result
Cremonesi Nu2002
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HM(HVKK) Result
Cremonesi Nu2002
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Comments on HM(HVKK)
Cremonesi Nu2002
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Reply to the comments on HM(HVKK)
Cremonesi Nu2002
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IGEX Canfranc
hep-ex 0202026
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Thermal detectors - Milano DB
Cremonesi Nu2002
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Milano DBD-II
Cremonesi Nu2002
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MDBD-II Results
Cremonesi Nu2002
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MDBD-II Background
Cremonesi Nu2002
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Proposed Experiments
Cremonesi Nu2002
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Proposed Experiments

• Half life normalised to 5 years operation

10s kg scale
Tonne scale

• Matrix element range. Half life for 50meV mass
  (in 1026y)

Elliott and Vogel Ann. Rev. Nucl. Part. Sci. 52
(2002)
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Modularity and prototyping

• Modularity
• Discrimination through segmentation
• Increase in support materials
• GENIUS vs. Majorana
• Systematics checks
• Prototyping
• Direct scale-up of current technology wont
  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

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NEMO-III
Cremonesi Nu2002
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NEMO-III
Cremonesi Nu2002
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CUORE
Cremonesi Nu2002
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CUORicino
Cremonesi Nu2002
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EXO - Xenon
Cremonesi Nu2002
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EXO - two approaches
Cremonesi Nu2002
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Majorana
Cremonesi Nu2002
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GENIUS
Cremonesi Nu2002
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GENIUS-TF
Cremonesi Nu2002
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GEM
Cremonesi Nu2002
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DCBA/COBRA
Cremonesi Nu2002
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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 (?) lt1 10kg Segmemtation Neutron background
CUORE TeO2 Bolometer Cuoricino approved No Not needed (34 natural) 0.2 1 tonne Active shield Segmentation Materials close to target
EXO LXe or Xe TPC Approved (Ba tag test, 100kg Lxe) No Needed lt2 10 tonne Co-location of daughter PSD Cost of enrichment Ba ion extraction
GENIUS Naked HPGe Genius-TF approved No G-TF natural G 86 enrichment 0.3 1 tonne PSD Cost of enrichment Use of LN Cosmogenics
Majorana HPGe 1 Ge det under construction No Needed (8 -gt 86) 0.3 420kg Segmentation PSD Cost of enrichment
MOON Mo Scintillator WLS/Scint/Mo testing No Yes 7 3 tonne (34 tonnes nat. Mo) Localisation High Q (3.03MeV) Resolution
NEMO Tracking chamber Scintillator NEMO-I/II Yes Yes 10 10kg Tracking Time of flight Magnetic field Radioisotopic impurity Scale-up?
TGV HPGe CaCO3 foils TGV 1 (1g) No Required (73) 0.2 ? TGV-2 10g Enrichment from CaF2 Mass
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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 gt10 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!
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Xenon experience in UK/RAL
Gotthard Xe TPC DB experiment (Roland)
ZEPLIN dark matter programme (RAL, IC, Shef)
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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 bb capability
• 124Xe (0.1 in nat. Xe) is one of seven known
  bb emitters
• 2nb b gives 4x 511keV photon signal
• 2nbEC gives X-ray (30keV) and 2x 511keV photon
  signal (
• 2nECEC gives 2x X-ray (30keV) signal
• Current limits for 124Xe are T0.52n gt 2x1014
  years, T0.50n gt 4x1017 years

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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 mans background.