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 well want to quantify the
  underlying physics.

3
Past Results
Elliott Vogel Annu. Rev. Part. Sci. 2002 52115
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)
5
Future Data Requirements

• Why wasnt 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

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

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.
8
Solar Scale showstoppers

• Need 100 tons of isotope
• Enrichment costs and production rates are not
  sufficient yet
• Will need RD 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 RD

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

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 RD 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.
• RD 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 RD
  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

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 well have at least a good outline by
  days end

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.

13
SignalBackground 11Its all about the
background
Degenerate
To reach atmospheric scale need BG on order 1/t-y.
Atmospheric
Solar
14
KKDC Claim
50 meV Or 1027 yr
Atmospheric Scale
Inverted
Solar Scale
Normal
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

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