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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.

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Double Beta Decay - status and future

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Double beta decay status and future

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

Double beta decay

Double Beta Decay

Cremonesi Nu2002

Bb0n rates

bb0n Rates

Cremonesi Nu2002

Why do bb0n

Why do bb0n?

Cremonesi Nu2002

Experimental considerations

Experimental Considerations

Measure this

Cremonesi Nu2002

Key issues

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

Current experimental limits

Current Experimental Limits

Cremonesi Nu2002

Current experimental limits1

Current Experimental Limits

Cremonesi Nu2002

Heidelberg moscow experiment

Heidelberg Moscow Experiment

Cremonesi Nu2002

Hm hvkk result

HM(HVKK) Result

Cremonesi Nu2002

Hm hvkk result1

HM(HVKK) Result

Cremonesi Nu2002

Comments on hm hvkk

Comments on HM(HVKK)

Cremonesi Nu2002

Reply to the comments on hm hvkk

Reply to the comments on HM(HVKK)

Cremonesi Nu2002

Igex canfranc

IGEX: Canfranc

hep-ex 0202026

Thermal detectors milano db

Thermal detectors - Milano DB

Cremonesi Nu2002

Milano dbd ii

Milano DBD-II

Cremonesi Nu2002

Mdbd ii results

MDBD-II: Results

Cremonesi Nu2002

Mdbd ii background

MDBD-II: Background

Cremonesi Nu2002

Proposed experiments

Proposed Experiments

Cremonesi Nu2002

Proposed experiments1

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)

Modularity and prototyping

Modularity and prototyping

  • Modularity

    • 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

Nemo iii


Cremonesi Nu2002

Nemo iii1


Cremonesi Nu2002



Cremonesi Nu2002



Cremonesi Nu2002

Exo xenon

EXO - Xenon

Cremonesi Nu2002

Exo two approaches

EXO - two approaches

Cremonesi Nu2002



Cremonesi Nu2002



Cremonesi Nu2002

Genius tf


Cremonesi Nu2002

Double beta decay status and future


Cremonesi Nu2002

Dcba cobra


Cremonesi Nu2002

Pros and cons

Pros and Cons

Bb0n and dark matter

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.


Xenon experience in uk ral

Xenon experience in UK/RAL

Gotthard Xe TPC DB experiment (Roland)

ZEPLIN dark matter programme

(RAL, IC, Shef)

Zeplin as bb0n experiment

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+ECgives X-ray (30keV) and 2x 511keV photon signal (

    • 2nECECgives 2x X-ray (30keV) signal

      • Current limits for 124Xe are T0.52n > 2x1014 years, T0.50n > 4x1017 years



  • 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….

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