NEMO 3 and SuperNEMO Hideaki OHSUMI (Saga Univ.) (NEMO/SuperNEMO - PowerPoint PPT Presentation

NEMO 3 and SuperNEMO Hideaki OHSUMI (Saga Univ.) (NEMO/SuperNEMO Collaboration) x 20 Sectors (Present) NEMO 3 is now runing at LSM Typical 2νββ events ~ every 2.5 minutes (Future) SuperNEMO Search for 0νββ events ! to find ν m (50meV?) Study neutrino mass ~0.2eV

PLAN PLAN • Short quick tour of NEMO-3 detector • Overview of 2 νββ results ( 100 Mo , 82 Se , 116 Cd, 150 Nd , 96 Zr 48 Ca) Single electron spectrum ( 100 Mo ) Decay to the excited 0 + ( 100 Mo ) • Phase I � Phase II (Low radon) and 0 νββ results • SuperNEMO

Philosophy of the NEMO- -3 experiment 3 experiment Philosophy of the NEMO Neutrinoless Double Beta Decays ( 0νββ) Majorana ν and effective mass <m ν > ? or new physics (SUSY) ? Measure several isotopes ( 0νββ, 2νββ) 100 Mo(~7kg) , 82 Se(~1kg) , 130 Te , 116 Cd, 96 Zr , 48 Ca , 150 Nd (no 76 Ge, 136 Xe) Tag and measure all the BG events e - , e + , γ , α , neutron → Tracking chamber+Calorimeter+B-field+Shields “zero background zero background” ” experiment experiment “ 2νββ 0 νββ : 2n → 2p+2e - (Δ L = 2 Process) (Beyond Standard Model) 0νββ (?) 2 νββ : 2n → 2p+2e - +2 ν (Standard Process) ν M E( β 1 + β 2 ) Q ββ

The Location of the NEMO3 The Location of the NEMO3 Frejus Underground NEMO 3 is here ! Laboratory Laboratoire Souterraine de Modane(LSM) (4800 m.w.e.) Italy France NEMO 3

The NEMO3 detector The NEMO3 detector Fréjus Underground Laboratory : 4800 m.w.e. Source : 10 kg of ββ isotopes cylindrical, S = 20 m 2 , e ~ 60 mg/cm 2 Tracking detector : drift wire chamber operating in Geiger mode (6180 cells) Gas: He + 4% ethyl alcohol + 1% Ar + 0.1% H 2 O Calorimeter : 1940 plastic scintillators coupled to low radioactivity PMTs Magnetic field: 25 Gauss Gamma shield: Pure Iron (e = 18cm) Neutron shield: 30 cm water (ext. wall) 40 cm wood (top and bottom) (since march 2004: water + boron) Able to identify e − , e + , γ and α

Cathodic rings Wire chamber PMTs Calibration tube Calibration Source scintillators 207 Bi 2e – (IC) lines ~0.5 ,~1 MeV 90 Sr ββ isotope foils 60 Co

ββ decay isotopes in NEMO ββ decay isotopes in NEMO- -3 detector 3 detector 05 04 06 03 ββ2ν measurement 02 07 116 Cd 405 g 08 01 Q ββ = 2805 keV 96 Zr 9.4 g 09 00 Q ββ = 3350 keV 150 Nd 37.0 g 19 10 Q ββ = 3367 keV 18 11 48 Ca 7.0 g Q ββ = 4272 keV 17 12 130 Te 454 g 13 16 14 15 Q ββ = 2529 keV External bkg 100 Mo 6.914 kg 82 Se nat Te 491 g 0.932 kg measurement Q ββ = 3034 keV Q ββ = 2995 keV Cu 621 g ββ0ν search (All the enriched isotopes produced in Russia)

Sources preparation

How detect signals and tag the background ? Identification of e, γ , α B=25G � Tracking (Identification e/others) source foil Signal Delayed (<700 μ s) α track Δ t ~ 0 ns β - β - � Calorimeter ε ( γ )~50% (@0.5MeV) ββ (0 ν ) decay Possible for tagging e γ , e γγ , e γγγ , … γ Internal background Source contaminations Δ t ~ 0 ns � Time of flight σ t ~300ps(@1MeV) e - β - α External Background rejection Δ t ~ 0 ns β - � Magnetic Field (Identification e - /e + ) β - ββ (2 ν ) decay 3~5% e - /e + confusion @ 1~7MeV External background Δ t ≥ 3 ns e - Study of Background Process « Crossing e - » γ � 214 Bi Tagged by e( γ ) α (~164 μ s) γ e - n Δ t ~ 0 ns ( 214 Bi-> 214 Po-> 210 Pb) e + or e - � 208 Tl e γ , e γγ , e γγγ , with γ (2.6MeV) e + e pairs - or Taggd by e( γ ) α (~300ns) Double Compton Compton + Möller ( 212 Bi-> 212 Po-> 208 Pb) � Neutron Crossing e (4~8MeV)

Background events observed by NEMO- -3 3… … Background events observed by NEMO Electron + α delay track (164 μ s) 214 Bi → 214 Po → 210 Pb Electron crossing > 4 MeV Neutron capture → Electron + N γ ’s 208 Tl (E γ = 2.6 MeV) Electron – positron pair B rejection

ββ events selection in NEMO-3 Typical ββ 2 ν event observed from 100 Mo Transverse view Transverse view Run Number: 2040 Run Number: 2040 Longitudinal Event Number: 9732 Event Number: 9732 view Longitudinal Date: 2003-03-20 Date: 2003-03-20 view Vertex 100 Mo foil emission Geiger plasma 100 Mo foil longitudinal Vertex propagation emission Deposited energy: E 1 +E 2 = 2088 keV Internal hypothesis: ( Δ t) mes –( Δ t) theo = 0.22 ns ( Δ vertex) // = 5.7 mm Common vertex: Scintillator ( Δ vertex) ⊥ = 2.1 mm + PMT Criteria to select ββ events: Trigger : at least 1 PMT > 150 keV ≥ 3 Geiger hits (2 neighbour layers + 1) • 2 tracks with charge < 0 • Internal hypothesis (external event rejection) • 2 PMT, each > 200 keV Trigger rate = 7 Hz • No other isolated PMT ( γ rejection) • PMT-Track association ββ events: 1 event every 2.5 minutes • No delayed track ( 214 Bi rejection)

100 Mo 2 β 2 ν preliminary results (Data Feb. 2003 – Dec. 2004) � (Phase I) Angular Distribution Sum Energy Spectrum 219 000 events 219 000 events NEMO-3 NEMO-3 6914 g 6914 g 100 Mo 100 Mo 389 days 389 days S/B = 40 S/B = 40 • Data 2 β 2 ν • Data Monte Carlo 2 β 2 ν Background subtracted Monte Carlo Background subtracted Cos( θ ) E 1 + E 2 (keV) T 1/2 = 7.11 ± 0.02 (stat) ± 0.54 (syst) × 10 18 y 7.37 kg.y Phys Rev Lett 95, 182302 (2005) No Significant discrepancy � 2 νββ is really standard process !

2 β 2 ν preliminary results for other nuclei NEMO-3 932 g T 1/2 = 9.6 ± 0.3 (stat) ± 1.0 (syst) × 10 19 y 82 Se 389 days 2750 events T 1/2 = 2.8 ± 0.1 (stat) ± 0.3 (syst) × 10 19 y 116 Cd 82 Se S/B = 4 150 Nd T 1/2 = 9.7 ± 0.7 (stat) ± 1.0 (syst) × 10 18 y • Data T 1/2 = 2.0 ± 0.3 (stat) ± 0.2 (syst) × 10 19 y 96 Zr 2 β 2 ν Monte Carlo Background subtracted Background subtracted E 1 +E 2 (keV) NEMO-3 NEMO-3 37 g 405 g NEMO-3 5.3 g 168.4 days 168.4 days 168.4 days 116 Cd 96 Zr 150 Nd 1371 events 449 events 72 events S/B = 7.5 S/B = 2.8 S/B = 0.9 Data Data Data ββ2ν ββ2ν ββ2ν simulation simulation simulation E 1 +E 2 (MeV) E 1 +E 2 (MeV) E 1 +E 2 (MeV)

48 Ca analysis 1st preliminary result 48 Ca analysis 1st preliminary result 1.07y 7g of 48 Ca enough radio pure after chemistry 214 Bi, 208 Tl but 30m Bq of 90 Sr! to remove Möller scattering pure beta emitter ( 90 Y) (1) E SUM >2.MeV or (2) Eth > 0.7 MeV cos θ < 0 back to back T 1/2 = [3.9 ± 0.7(stat) ± 0.6(syst)]·10 19 y 300 20 18 250 16 14 200 12 150 10 8 100 6 4 50 2 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 E SUM (MeV) ( 48 Ca-foil) E SUM (MeV) ( 48 Ca-foil,E Small > 0.7 MeV, cos( θ ) < 0.0 ) Esmall > 0.7 MeV cos (θ)< 0.0 Esmall > 0.2 MeV

Single electron spectum 2νββ ( 100 Mo) SSD simulation T 1/2 = 7.11 ± 0.02 (stat) ± 0.54 (syst) × 10 18 y Phys. Rev. Lett. 95 (2005) 182302 SSD model confirmed HSD , higher levels contribute to the decay 1 + SSD , 1 + level 100 Tc dominates in the decay 0 + (Abad et al., 1984, Ann. Fis . A 80, 9) 100 Mo Single electron spectrum different between SSD and HSD Simkovic, J. Phys. G , 27, 2233, 2001 E single (keV)

Decay to the excited 0 + ( 100 Mo 2νββ ) Decay to the excited 0 + state (1130keV) of 100 Ru -0.9 (stat) ± 0.8 (syst) × 10 20 y T 1/2 = 5.7 +1.3 Nuclear Physics A781 (2006) 209-226.

ββ 0 ν Analysis: Background Measurement ββ 0 ν Analysis: Background Measurement Radon in the NEMO-3 gas of the wire chamber Due to a tiny diffusion of the radon of the laboratory inside the detector A(Radon) in the lab ~15 Bq/m 3 β − α 214 Bi → 214 Po (164 μ s) → 210 Pb Two independant measurements of radon in NEMO-3 gas 222 Rn (3.8 days) � Radon detector at the input/output of the NEMO-3 gas ~ 20 counts/day for 20 mBq/ m 3 � (1e − + 1 α ) channel in the NEMO-3 data : β − 214 Po 218 Po β Delayed tracks (<700 μ s) to tag delayed α from 214 Po Decay α delayed 214 Bi → 214 Po (164 μ s) → 210 Pb in gas 214 Bi 164 μ s α ~ 200 counts/hour for 20 mBq/m 3 210 Pb 214 Pb Good agreement between the two measurements A(Radon) in NEMO-3 ≈ 20-30 mBq/m 3 ~ 1 ββ0ν -like events/year/kg with 2.8 < E 1 +E 2 < 3.2 MeV Radon is the dominant background at Phase 1 for ββ0ν search in NEMO-3 !!!

Free- -Radon Air factory Radon Air factory Free Starts running Oct. 4 th 2004 in Modane Underground Lab. 1 ton charcoal @ -50 o C, 7 bars Activity: A( 222 Rn) < 15 mBq/m 3 !!! Flux: 125 m 3 /h a factor 1000

NEMO Tent for Free- NEMO Tent for Free -Radon air Installation Radon air Installation May 2004 : Tent surrounding the detector Phase I � Phase II

Preliminary results with 100 Mo (7 kg) 0νββ Phase I, High radon Phase II, Low radon Phase I + II 394 days 299 days 693 days Number of events / 40 keV Number of events / 40 keV Number of events / 40 keV NEMO 3 NEMO 3 NEMO 3 [2.8-3.2] MeV: ε ( ββ0ν ) = 8 % [2.8-3.2] MeV: ε ( ββ0ν ) = 8 % Expected bkg = 3.0 events Expected bkg = 8.1 events N observed = 4 events N observed = 7 events T 1/2 ( ββ0ν ) > 5.8 x 10 23 (90 % CL) <m ν > < 0.6 – 2.4 eV Phases I + II (preliminary) T 1/2 ( ββ0ν ) > 2 x 10 24 (90 % CL) <m ν > < 0.3 – 1.3 eV expected in 2009