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Neutrinoless doublebeta decay and the SuperNEMO project'

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Operates at the Fr jus Underground Laboratory in Savoie, France ... NEMO3 contains 10kg of isotopes primarily including enriched molybdenum (6.9kg) ... – PowerPoint PPT presentation

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Title: Neutrinoless doublebeta decay and the SuperNEMO project'


1
Neutrinoless double-beta decay and the SuperNEMO
project.
  • Darren Price
  • University of Manchester
  • http//www.hep.man.ac.uk/u/darren

24 November, 2004
2
What is the NEMO project?
  • NEMO Neutrino Ettore Majorana Observatory
  • Main function is investigating neutrinoless
    double-beta decay (0?bb) (also 2?bb)
  • Operates at the Fréjus Underground Laboratory in
    Savoie, France
  • NEMO Collaboration working since 1989
  • NEMO prototypes
  • NEMO3 design began 1994
  • about where we are now with SuperNEMO
  • Planned to be running until 2007-8 when
    hopefully(!) superseded by SuperNEMO

3
What is the NEMO project?
  • Experimentally the double beta decays only
    distinguished by their different electron energy
    spectra
  • Constructed to detect emitted electrons from
    isotopes known to produce double beta decay,
    whilst reducing any background effects.

4
What is the NEMO project?
  • NEMO3 contains 10kg of isotopes primarily
    including enriched molybdenum (6.9kg)
  • Need to measure and tag all types of background
  • same principles in SuperNEMO, need to eliminate
    BG
  • ltmvgt sensitivity (0.15-0.5)
    eV
  • 0?bb observation gives information about absolute
    mass scale

5
What is neutrinoless double-beta decay?
  • Double beta decay - nucleus simultaneously
    releases two electrons either with two or no
    neutrinos in the final state
  • In 2?bb, two neutrinos observed, satisfies lepton
    number conservation
  • In 0?bb, no neutrinos - implications for Standard
    Model

6
What is neutrinoless double-beta decay?
  • Despite lepton no. violation, 0?bb could exist
    if
  • Neutrinos had non-zero mass (yes)
  • Neutrinos are Majorana particles
  • Prevailing belief - 0?bb exists, good
    experimental indications, and preferred by
    theorists!
  • Other processes can explain 0?bb, but only 0?bb
    can test Majorana nature of neutrino with
    absolute mass scale
  • 0?bb only practical approach to tell if Majorana
    neutrino exists!

7
What is neutrinoless double-beta decay?
  • Half life of 0?bb given by
  • Gives ltmvgt - estimation of neutrino mass scale
  • Electron energy plot for 2?bb and 0?bb

8
What is SuperNEMO?
  • SuperNEMO is next generation 0?bb detector
  • Much larger design - 100kg isotope (Se-82)
  • planar geometry, 4 supermodules
  • low BG, 5000 photomultipliers, passive shielding
  • 10xNEMO3 (big detector - disadvantage)
  • NEMO3 is testing feasibility for SuperNEMO
  • need BG only from 2?
  • need DE/E10 at 1MeV (better than NEMO3)
  • demonstrated at UCL/Dubna

9
What is SuperNEMO?
  • Boulby mine - attractive experimental site
  • Timescale
  • 2004-05 Scintillator RD
  • 2005-06 Design proposal and prototype
  • 2007-10 Production
  • 2009-10 Start taking data
  • 2014 Planned sensitivity
  • ltmvgt sensitivity 0.04eV

10
What am I doing?
  • New experiment - new problems
  • Figuring out how GEANT models 0?bb/2?bb including
    decay kinematics
  • Detector geometry materials (tracking,
    scintillator)
  • Backscattering results
  • Energy resolution

11
Considerations
  • ?-ray effects
  • BG and energy resolution
  • Mechanics of detection
  • lasers for daughter particle?
  • wires to track electrons?
  • Active/passive scintillator?

12
Some results so far...
  • Backscattered electrons
  • percentage backscattered
  • energy distribution

13
Some results so far...
14
Some results so far...
15
Neutrinoless double-beta decay and the SuperNEMO
project.
  • Darren Price
  • University of Manchester
  • http//www.hep.man.ac.uk/u/darren

24 November, 2004
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