2. Double Beta Decay L=2 2: (A,Z)  (A,Z+2) + 2e- + 2ne
(Observed for several nuclei,
test of nuclear matrix elem.
calculations)
L=2
0: (A,Z)  (A,Z+2) + 2e- d u e- W- ne
1/t = G(Q,Z) |Mnucl|2 mee2,
mee = |i Uei ² mi |

3. Range of mee derived from solar and atmospheric oscillation experiments
mee = f(m1, m²sol, m²atm, 12 , 13, -)
from oscillation experiments
F.Feruglio,
A. Strumia,
F. Vissani,
NPB 637
Inverted hierarchy
Normal hierarchy
Degenerate
Lightest neutrino (m1) in eV
| mee| in eV
90% CL
Negligible
errors from
oscillations;
width due to
CP phases
Goal of next
generation
experiments:
~10 meV
Lower bounds!

4. 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 = 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 = keV
NB: More than one nuclei needed to check systematics from nuclear matrix elements

5. NEMO3 Start data taking February 2003 Source in form of foils:
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

6. NEMO3: first results t1/22n (y) = 7.8 ± 0.09 stat ± 0.8 syst  1018 y
First results on 100Mo (650 h)
V. Vasiliev
(Nemo coll.) 2n
spectrum
t1/22n (y) = 7.8 ± 0.09 stat ± 0.8 syst  y
t1/20n (y) > 6  y
Expected final sensitivity:
0.2 – 0.4 eV (6.9 kg)
mee < 1.8 – 2.9 eV
(C. Augier, ECT Trento)

7. CUORICINO 0.8 m Start data taking february 2003
Energy resolution: 7 keV FWHM
TeO2 (40 kg)  130Te (13 kg): Q = 2615 keV
2615 keV 208Tl
single escape 208Tl
double escape 208Tl
Calibration spectrum
0.8 m
(A. Giuliani, Taup03)

8. CUORICINO: first results
anticoincidence
background spectrum,
only 5x5x5 crystals
Background level
0.23 .04 c/keV/kg/y
t1/20n > 5  y
mee < 0.58 – 1.4 eV
(90% c.l.)
3 y sensitivity (with present performance):
1  1025 y  mee < 0.13 – 0.31 eV
(A. Giuliani, Taup03)

10. New concept under study: Ge in liquid Ar – new ideas
Replace LN (LN=0.8 g/cm³, 77 K)
by LAr (LN=1.4 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, …
What’s about Ar-39, Ar-42 ?

11. 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:
M·T = 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

12. 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-Kleingrothaus, J. Hellmig, M. Hirsch (1997); H.V. Klapdor–Kleingrothaus, L. Baudis, G. Heusser, B. Majorovits, H. Paes (1999), hep-ph/

13. LN2 shield against external background radiation
LNGS: ~ 107 /m²/d
(2.6 MeV )
~6 m
10-4 (kg keV y) -1
LN2

14. LNGS
~14 m
14.80 m

15. LN/LAr facility: Design study (b)

17. How small could a tank be?
Lead layer submersed in LAr
232Th activity of lead  tank Ø
Preliminary results 30Bq/kg 

18. 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]

19. 60Co: no vs. active suppression
Reduction factor ~100
Reflector (VM2000)
Wavelength shifter
,

20. Bgd. in LAr: example 42Ar
42Ar / natAr = 3· (30 Bq/kg) [Barabash et al., LNGS]

21. 42Ar: no vs. active suppression
Reflector (VM2000)
Wavelength shifter
, 1,2
No issue for DBD even without active suppression!

22. External bgd: example 2.615 MeV gamma 232Th (208Tl) in lead shield
Flux from rocks(0.5 Bq / kg) and
concrete (5 Bq / kg) @ LNGS: 3.5 ·107 / (m² d) [BOREXINO, Laubenstein]
New lead for shielding under study
with LNGS: <30 Bq / kg

23. 232Th (208Tl): no vs. active suppr.
Reflector (VM2000)
Wavelength shifter 
Lead
Simulation for 30 Bq/kg, inner-Ø: 2m, height: 2 m

24. 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: eV, DG: <1 eV (90% CL))
Second generation experiments (NEMO3, CUORICINO) started data taking; sensitive to check HdM claim within next years: ~ eV