Transcript Slide 1

Double Beta Decay
2: (A,Z)  (A,Z+2) + 2e- + 2e
(Observed for several nuclei,
test of nuclear matrix elem.
calculations)
0: (A,Z)  (A,Z+2) + 2eu
d
WW-
d
u
ee
L=2
e
e-
1/t = G(Q,Z) |Mnucl|2 mee2,
mee = |i Uei ² mi |
Range of mee derived from solar and
atmospheric oscillation experiments
mee = f(m1, m²sol, m²atm, 12 , 13, -)
Goal of next
generation
experiments:
~10 meV
| mee| in eV
from oscillation experiments
F.Feruglio,
A. Strumia,
F. Vissani,
NPB 637
Inverted hierarchy
90% CL
Normal hierarchy
Lower bounds!
Lightest neutrino (m1) in eV
Negligible
errors from
oscillations;
width due to
CP phases
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
NEMO3
• Source in form of foils:
• Tracking volume with Geiger cells
• e+/e- separation by magnetic field
1 SOURCE
2 TRACKING VOLUME
3 CALORIMETER
• Plastic scintillators for calorimetry and timing
Start data taking February 2003
NEMO3: first results
First results on 100Mo (650 h)
V. Vasiliev
(Nemo coll.)
2
spectrum
t1/22 (y) = 7.8 ± 0.09 stat ± 0.8 syst  1018 y
t1/20 (y) > 6  1022 y
Expected final sensitivity:
0.2 – 0.4 eV (6.9 kg)
mee < 1.8 – 2.9 eV
(C. Augier, ECT Trento)
CUORICINO
Start data taking february 2003
Energy resolution: 7 keV FWHM
TeO2 (40 kg)  130Te (13 kg):
Q = 2615 keV
0.8 m
2615 keV 208Tl
Calibration spectrum
single escape 208Tl
double escape 208Tl
(A. Giuliani, Taup03)
CUORICINO: first results
anticoincidence
background spectrum,
only 5x5x5 crystals
Background level
0.23 .04
c/keV/kg/y
3 y sensitivity (with present performance):
1  1025 y  mee < 0.13 – 0.31 eV
t1/20 > 5  1023 y
mee < 0.58 – 1.4 eV
(90% c.l.)
(A. Giuliani, Taup03)
New concept under study: Ge in
liquid Ar – new ideas
• Replace
by
LN ( LN=0.8 g/cm³, 77 K)
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 ?
76Ge:
sensitivity, exposure and
background
HEIDELBERG-MOSCOW Collaboration,
Eur. Phys. J. A 12 (2001) 147:
M·T = 35.5 kg y, b = 6 ·10-2
E ~ 4.2 keV
(kg y keV),
Sensitivity (with bgd):
mee  (b E / M T)1/4
Basic concepts about 76Ge in
liquid N2
Operation of ‘naked’ Ge-detecctors In liquid
nitrogen: G. Heusser, Ann. Rev. Nucl. Part.
Sci. (1995)
GENIUS proposal: H.V. KlapdorKleingrothaus, J. Hellmig, M. Hirsch (1997);
H.V. Klapdor–Kleingrothaus, L. Baudis, G.
Heusser, B. Majorovits, H. Paes (1999),
hep-ph/9910205
• background sources
external to crystals
• clean contacts and support
can be realized
• minimization of surface
contaminations
• purification of liquid
nitrogen
LN2 shield against external
background radiation
LNGS: ~ 107 /m²/d
(2.6 MeV )
~6 m
10-4 (kg keV y) -1
LN2
Space @ LNGS
~14 m
14.80 m
LN/LAr facility: Design study (b)
How small could a tank be?
• Lead layer submersed
in LAr
•
232Th
activity of lead
 tank Ø
• Preliminary results
30Bq/kg

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]
60Co:
no vs. active suppression
,
Wavelength shifter Reflector (VM2000)
Reduction factor ~100
Bgd. in LAr: example 42Ar
42Ar
/ natAr = 3·10-21 (30 Bq/kg)
[Barabash et al., LAr-TPC @ LNGS]
42Ar:
no vs. active suppression
, 1,2
Wavelength shifter
Reflector (VM2000)
No issue for DBD even without active suppression!
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)
New lead for shielding under study
with GEMPI @ LNGS:
<30 Bq / kg
[BOREXINO, Laubenstein]
232Th (208Tl):
no vs. active suppr.

Wavelength shifter Reflector (VM2000)
Lead
Simulation for 30 Bq/kg, inner-Ø: 2m, height: 2 m
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: <1 eV (90% CL))
Second generation experiments (NEMO3, CUORICINO)
started data taking; sensitive to check HdM claim within next
years: ~ 0.1-0.4 eV