Double Beta Decay

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Double Beta Decay
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Range of mee derived from solar and atmospheric
oscillation experiments
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Experimental status of running experiments
Heidelberg Moscow MPIK Heidelberg, Kurchatov
Institute Location Gran Sasso Underground
Laboratory Source detector, 76Ge (10.9 kg
isotopically enriched ( 86)) Q 2038 keV
CUORICINO (Cryogenic Underground Observatory for
Rare Events) Firenze, Gran Sasso, Insubria,
LBNL, Leiden, Milano, Neuchatel, South Carolina,
Zaragoza Location Gran Sasso Underground
Laboratory Source detector, TeO2 (40 kg) ?
130Te (13 kg) Q 2615 keV
NEMO3 (Neutrino Ettore Majorana Observatory)
CENBG Bordeaux, Charles Univ. Prague, FNSPE
Prague, INEEL, IReS Strasbourg, ITEP Moscow, JINR
Dubna, Jyvaskyla Univ., LAL Orsay, LPC Caen, LSCE
Gif, Mount Holyoke College, Saga Univ, UCL
London Location Frejus Underground
Laboratory Source ? detector ? study of different
nuclei main target 100Mo (6.9 kg) Q 3034 keV
NB More than one nuclei needed to check
systematics from nuclear matrix elements
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NEMO3

• Source in form of foils

1 SOURCE 2 TRACKING VOLUME 3 CALORIMETER

• Tracking volume with Geiger cells
• e/e- separation by magnetic field
• Plastic scintillators for calorimetry and timing

Start data taking February 2003
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NEMO3 first results
First results on 100Mo (650 h)
V. Vasiliev (Nemo coll.)
2n spectrum
t1/22n (y) 7.8 0.09 stat 0.8 syst ? 1018
y
t1/20n (y) gt 6 ? 1022 y
Expected final sensitivity 0.2 0.4 eV (6.9 kg)
mee lt 1.8 2.9 eV
(C. Augier, ECT Trento)
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CUORICINO
Start data taking february 2003 Energy
resolution 7 keV FWHM TeO2 (40 kg) ? 130Te (13
kg) Q 2615 keV
Calibration spectrum
0.8 m
(A. Giuliani, Taup03)
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CUORICINO first results
t1/20n gt 5 ? 1023 y mee lt 0.58 1.4 eV (90
c.l.)
3 y sensitivity (with present performance) 1 ?
1025 y ? mee lt 0.13 0.31 eV
(A. Giuliani, Taup03)
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New concept under study Ge in liquid Ar new
ideas

• Replace LN (??LN0.8 g/cm³, 77 K)
• by LAr (??LN1.4 g/cm³, 87 K)
• ? ?LAr/ ?LN (2.615 MeV) 0.62
• Scintillation yield 40,000 photons / MeV ?
  Active shielding medium!
• (4 x organic liquid scintillator) Emission in XUV
  (130 nm)
• Wavelength shifting required Organic WLS or Xe
  addition
• Essential for cosmogenic activities Co-60,
  Ge-68,
• Whats about Ar-39, Ar-42 ?

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76Ge sensitivity, exposure and background
0.0001
0.001
0.01
0.06 / (kg year keV)
HEIDELBERG-MOSCOW Collaboration, Eur. Phys. J. A
12 (2001) 147 MT 35.5 kg y, b 6 10-2 (kg y
keV), DE 4.2 keV
Sensitivity (with bgd) mee ? (b DE / M T)1/4
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Basic concepts about 76Ge in liquid N2

• background sources external to crystals
• clean contacts and support can be realized
• minimization of surface contaminations
• purification of liquid nitrogen

Operation of naked Ge-detecctors In liquid
nitrogen G. Heusser, Ann. Rev. Nucl. Part. Sci.
(1995) GENIUS proposal H.V. Klapdor-Kleingrothau
s, J. Hellmig, M. Hirsch (1997) H.V.
KlapdorKleingrothaus, L. Baudis, G. Heusser, B.
Majorovits, H. Paes (1999), hep-ph/9910205
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LN2 shield against external background radiation
LNGS ? 107 /m²/d (2.6 MeV ?)
6 m
10-4 (kg keV y) -1
LN2
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Space _at_ LNGS
14 m
14.80 m
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LN/LAr facility Design study (b)
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How small could a tank be?

• Lead layer submersed in LAr
• 232Th activity of lead ? tank Ø
• Preliminary results ?30?Bq/kg ?

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Active suppression of internal bgd example 60Co

• Cosmogenic activities
• Production after completion of crystal growth
• Exposure to cosmic rays above ground for 10 days
  0.18 ?Bq/kg GENIUS

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60Co no vs. active suppression
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Bgd. in LAr example 42Ar
42Ar / natAr 310-21 (30 ?Bq/kg)
Barabash et al., LAr-TPC _at_ LNGS
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42Ar no vs. active suppression
?, ?1,?2
No issue for DBD even without active suppression!
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External bgd example 2.615 MeV gamma 232Th
(208Tl) in lead shield
Flux from rocks(0.5 Bq / kg) and concrete (5 Bq
/ kg) _at_ LNGS 3.5 107 / (m² d) BOREXINO,
Laubenstein New lead for shielding under study
with GEMPI _at_ LNGS lt30 ?Bq / kg
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232Th (208Tl) no vs. active suppr.
?
Lead
Simulation for 30 ?Bq/kg, inner-Ø 2m, height 2 m
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Summary and outlook (1)

• DBD unique tool to study neutrino properties
  Majorana vs. Dirac, mass scale, hierarchy, CP
  phases
• Oscillation data make distinct predictions for
  mee (NH 1-4 meV, IV 14-57 eV, DG lt1 eV (90
  CL))
• Second generation experiments (NEMO3, CUORICINO)
  started data taking sensitive to check HdM claim
  within next years 0.1-0.4 eV

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