Double Beta Decay 2 : (A,Z) (A,Z+2) + 2e - + 2 e (Observed for several nuclei, test of nuclear...
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Transcript of Double Beta Decay 2 : (A,Z) (A,Z+2) + 2e - + 2 e (Observed for several nuclei, test of nuclear...
Double Beta Decay
2: (A,Z) (A,Z+2) + 2e- + 2e(Observed for several nuclei, test of nuclear matrix elem. calculations)
L=2
0: (A,Z) (A,Z+2) + 2e-
d
d
u
u
e-
e-
W-
W- e
e
= G(Q,Z) |Mnucl|2 mee2, mee = |i Uei ² mi |
Range of mee derived from solar and atmospheric oscillation experiments
Goal of next generation experiments:~10 meV
F.Feruglio, A. Strumia, F. Vissani, NPB 637
Inverted hierarchy
Normal hierarchy
Degen
erat
e
Lightest neutrino (m1) in eV
| mee
| in
eV
90% CL
Negligible errors from oscillations;width due toCP phases
Lower bounds!
mee = f(m1, m²sol, m²atm, 12 , 13, -)from oscillation experiments
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
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
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
NB: More than one nuclei needed to check systematics from nuclear matrix elements
NEMO3
• Tracking volume with Geiger cells
• e+/e- separation by magnetic field
• Plastic scintillators for calorimetry and timing
1 SOURCE
2 TRACKING VOLUME
3 CALORIMETER
• Source in form of foils:
Start data taking February 2003
NEMO3: first resultsFirst results on 100Mo (650 h)
/22 (y) = 7.8 ± 0.09 stat ± 0.8 syst 1018 y
/20 (y) > 6 1022 y
mee < 1.8 – 2.9 eV
Expected final sensitivity: 0.2 – 0.4 eV (6.9 kg)
2spectrum
V. Vasiliev (Nemo coll.)
(C. Augier, ECT Trento)
CUORICINO
2615 keV 208Tl
single escape 208Tl
double escape 208Tl
Start data taking february 2003Energy resolution: 7 keV FWHMTeO2 (40 kg) 130Te (13 kg): Q = 2615 keV
0.8
m Calibration spectrum
(A. Giuliani, Taup03)
CUORICINO: first results
/20 > 5 1023 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
anticoincidence background spectrum,
only 5x5x5 crystalsBackground level
0.23 .04
c/keV/kg/y
(A. Giuliani, Taup03)
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 ?
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 (kg y keV),E ~ 4.2 keV
Sensitivity (with bgd): mee (b E / M T)1/4
0.06 / (kg year keV)
0.01
0.001
0.0001
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/9910205
LN2 shield against external background radiation
LNGS: ~ 107 /m²/d (2.6 MeV )
LN2
~6 m
10-4 (kg keV y) -1
Space @ LNGS
14.80 m
~14 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 30Bq/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
,
Reflector (VM2000)Wavelength shifter
Reduction factor ~100
Bgd. in LAr: example 42Ar42Ar / natAr = 3·10-21 (30 Bq/kg) [Barabash et al., LAr-TPC @ LNGS]
42Ar: no vs. active suppression
, 1,2
No issue for DBD even without active suppression!
Reflector (VM2000)Wavelength shifter
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 GEMPI @ LNGS: <30 Bq / kg
232Th (208Tl): no vs. active suppr.
Lead
Simulation for 30 Bq/kg, inner-Ø: 2m, height: 2 m
Reflector (VM2000)Wavelength shifter
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