Stefano Torre University College London for NEMO3 and SuperNEMO collaborations Half day IoP Meeting 12 Oct 2011 Outline • 0νββ and 2νββ • Observation technique • Nemo-3 Results • SuperNEMO design and construction Double beta decay with NEMO3 and SuperNEMO
Outline 0νββ and 2νββ Observation technique Nemo-3 Results SuperNEMO design and construction. Double beta decay with NEMO3 and SuperNEMO. Stefano Torre University College London for NEMO3 and SuperNEMO collaborations Half day IoP Meeting 12 Oct 2011. - PowerPoint PPT Presentation
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Stefano Torre
University College London
for NEMO3 and SuperNEMO collaborations
Half day IoP Meeting
12 Oct 2011
Outline
•0νββ and 2νββ•Observation technique•Nemo-3 Results•SuperNEMO design and construction
Double beta decay with NEMO3 and SuperNEMO
2S.Torre - Double beta decays with NEMO3 and SuperNEMO - 12/10/2011
Which process cause the double beta decay? But η can be due to mass mechanism, V+A,
majoron, SUSY, ... with different topology in the final state
θ - angle between e1 and e2
E1 - single e- energy, keV
〈 mν 〉 V+A
3S.Torre - Double beta decays with NEMO3 and SuperNEMO - 12/10/2011
Measuring the Lepton Violating parameter
IsotopeQββ, MeV
48Ca4.27
76Ge2.04
82Se3.0
96Zr3.35
100Mo3.03
116Cd2.8
130Te2.53
136Xe2.48
150Nd3.37
G0ν
×10-15 yr-1
75.8 7.6 33,5 69.7 54.5 58.9 52.8 56.3 249
Phase space factor
• phase space is known• half life is measured• need to know the Nuclear Matrix
Element (NME)• variation between models and
Isotopes• combine measurement from as many
isotopes as possible
4S.Torre - Double beta decays with NEMO3 and SuperNEMO - 12/10/2011
NEMO3
ββ isotope foils
PMT
cathode rings wire chamber
Plasticscintillator
• use calorimeter for energy and time measurement
• use tracker for full event reconstruction
• identify e-, e+, ɣ, α• 10 kg of ββ isotopes:
• 7kg 100Mo • 1kg 82Se
• smaller quantities of 116Cd, 150Nd, 48Ca, 96Zr, 130Te
5S.Torre - Double beta decays with NEMO3 and SuperNEMO - 12/10/2011
NEMO3
• source distributed on cylindrical surface
• drift wire chamber operated in geiger mode (6180 cells)• He + 4% ethyl alcohol + 1% Ar +
0.1%H2O
• calorimeter made of 1940 plastic scintillators coupled to low radioactivity PMTs
• Magnetic field: 25 Gauss• Gamma shield: iron• Neutron shield:
• 30cm borated water (external wall)• 40cm wood (top and bottom)
6S.Torre - Double beta decays with NEMO3 and SuperNEMO - 12/10/2011
NEMO3
LSM Modane, France(Tunnel Frejus, depth of ~4,800 mwe )
7
Selection of ββ events
S.Torre - Double beta decays with NEMO3 and SuperNEMO - 12/10/2011
foil of100Mo
vertex
scintillator
track
vertex
Run : 3478Event: 6930Date: 09/11/2004
(Δvertex)⁄⁄ = 3 cm
• 2 tracks with charge < 0• 2 PMT, each > 200 keV• PMT-Track association • Common vertex
• Internal hypothesis (external event rejection)• No other isolated PMT (γ rejection)• No delayed track (214Bi rejection)
Criteria to select ββ events
1 ββ event every 2,5 minutes
Top view Side view
8S.Torre - Double beta decays with NEMO3 and SuperNEMO - 12/10/2011
Backgrounds
External
Internal
Background measurement in NEMO-3: NIM A606 (2009) 449
• Natural radioactivity• 238U, 232Th, 40K, Rn
• Cosmics
• neutrons
9S.Torre - Double beta decays with NEMO3 and SuperNEMO - 12/10/2011
Background: Rn activityMeasurements of 222Rn activity in the gas of tracker (mBq/m3)
T1/2 = 162.9μs
Delay time of the α track (μs)
214Bi → 214Po (164 μs) → 210Pb
10S.Torre - Double beta decays with NEMO3 and SuperNEMO - 12/10/2011