The  Experimental Program

1. The Experimental Program Steve Elliott

2. An exciting experimental program • Experimental techniques • General requirements • Discovery vs. measurement • Required number of measurements and their precision If we see , the qualitative physics results are profound, but next we’ll want to quantify the underlying physics. Steve Elliott/double beta decay working group

3. Elliott & Vogel Annu. Rev. Part. Sci. 2002 52:115 Past Results Steve Elliott/double beta decay working group

4. A Recent Claimhas become a litmus test for future efforts  is the search for a very rare peak on a continuum of background. ~70 kg-years of data 13 years The “feature” at 2039 keV is arguably present. NIM A522, 371 (2004) Steve Elliott/double beta decay working group

5. Future Data Requirements Why wasn’t this claim sufficient to avoid controversy? • Low statistics of claimed signal - hard to repeat measurement • Background model uncertainty • Unidentified lines • Insufficient auxiliary handles Result needs confirmation or repudiation Steve Elliott/double beta decay working group

6. Various Levels of Confidence • A preponderance of the evidence: a combination of • Correct peak energy • Single-site energy deposit • Proper detector distributions (spatial, temporal) • Rate scales with isotope fraction • Open and shut case: include the following • Observe the two-electron nature of the event • Measure kinematic dist. (energy sharing, opening angle) • Observe the daughter • Observe the excited state decay • Beyond a reasonable doubt: the smoking gun • See the process in several isotopes Steve Elliott/double beta decay working group

7. Discovery vs. Measurementa future decision point These two goals may require different technical approaches. As yet, there is no viable proposal for an experiment sensitive to the solar scale. Steve Elliott/double beta decay working group

8. Solar Scale: showstoppers • Need 100 tons of isotope • Enrichment costs and production rates are not sufficient yet • Will need R&D to improve capability • Need excellent energy resolution • Better than 1% FWHM • Perhaps an experiment with 106 solid state detectors is possible • Cost/detector will need to be greatly reduced • Large multi-element detector electronics are improving • Metal loaded liquid scintillator or Xe techniques scale more easily and cost effectively, but resolution requires R&D Steve Elliott/double beta decay working group

9. Need several, precise experiments • Values of the double beta decay rate from several nuclei will help untangle the underlying physics • 3-4 experiments • Several values are only useful, if the measurements are “precise” • 10-20% uncertainty • Different techniques are also required • No one technique can provide all the characteristics of a “perfect” experiment Steve Elliott/double beta decay working group

10. Our White Paper • Science (draft could be written beforehand) 1-2 pages • Priority for first suite of experiments 1/2 page • science goals, not specific experiment technology • Proof-of-principle R&D vs. ready-to-go technologies • Roadmap (rough order of magnitude of cost + time frame) 1 page • A rough guess as to the cost and schedule of any first-suite experimental program. • R&D needs 1/2 page • An estimate of the cost to determine engineering/costing/scheduling for the initial suite of experiments proposed for DUSEL itself in time for the MRE-FC submission; in addition, we also need to know ongoing proof-of-principle R&D costs. • How to arrive at realistic cost and schedules 1/2 page • If an experiment (or goal) clearly can not make the MRE-FC timescale, we should indicate so. • Education and Outreach 1/2 page • What is our subfields opportunities Steve Elliott/double beta decay working group

11. Our Plan • Hear from the community about various ideas for double beta decay • Discuss these proposals in context of our white paper • Begin work on the white paper in “public” to maximize community input • Hopefully we’ll have at least a good outline by day’s end Steve Elliott/double beta decay working group

12. Underlying (0) Mechanisms • There are many physics models that lead to Lepton Number Violation (), |M| can change with the model • Light neutrino exchange • Heavy neutrino exchange • R-parity violating supersymmetry • RHC • etc. Steve Elliott/double beta decay working group

13. Signal:Background ~ 1:1Its all about the background Degenerate To reach atmospheric scale need BG on order 1/t-y. Atmospheric Solar Steve Elliott/double beta decay working group

14. KKDC Claim 50 meV Or ~ 1027 yr Atmospheric Scale Inverted Solar Scale Normal Steve Elliott/double beta decay working group

15. An Ideal ExperimentMaximize Rate/Minimize Background Large Mass (~ 1 ton) Large Q value, fast bb(0n) Good source radiopurity Demonstrated technology Ease of operation Natural isotope Small volume, source = detector Good energy resolution Slow bb(2n) rate Identify daughter in real time Event reconstruction Nuclear theory Steve Elliott/double beta decay working group

16. Great Number of Proposed Experiments • Calorimeter • Semi-conductors • Bolometers • Crystals/nanoparticles immersed in scintillator • Tracking • Liquid or gas TPCs • Thin source with wire chamber or scintillator Steve Elliott/double beta decay working group