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NEMO-3 Detector Preliminary results Performance of the detector

Journées Neutrinos 27-28 novembre 2003 LPNHE-Paris. NEMO Experiment Neutrino Ettore Majorana Observatory. NEMO-3 Detector Preliminary results Performance of the detector 2b2n analysis for 100 Mo, 82 Se and 150 Nd Background study for 2b0n research ( 208 Tl and Radon)

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NEMO-3 Detector Preliminary results Performance of the detector

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  1. Journées Neutrinos 27-28 novembre 2003 LPNHE-Paris NEMO Experiment Neutrino Ettore Majorana Observatory • NEMO-3 Detector • Preliminary results • Performance of the detector • 2b2n analysis for 100Mo, 82Se and 150Nd • Background study for 2b0n research (208Tl and Radon) • Future of NEMO Xavier Sarazin for NEMO Collaboration

  2. NEMO Experiment Neutrino Ettore Majorana Observatory • Search for neutrinoless double beta decay • Study several isotopes • Mo100 , Se82 , Te130 , Cd116 , Zr96 , Ca48 , Nd150 • Tag and measure all the components of background • e-, e+, g, a, neutrons “zero background” experiment

  3. ( ) Double beta bb(0n) decay : Physics beyond the standard model • DL = 2 Process • Majorana Neutrino n =n and effective mass <mn> • Right-handed current in weak interaction • Majoron emission • SUSY particle exchange bb(0n) : 2n  2p+2e- p n W- e- neR h nM neL h e- W- n p (Qbb ~ MeV)

  4. NEMO-3 Detector Located in Modane Underground Laboratory • Sources: 20 m2, total mass ~ 10 kg, thickness ~ 60 mm • Tracking detector(6180 Geiger cells in He+alcohol): Vertex st=5 mm, sz = 1 cm • Calorimeter(1940 plastic scintillators+ PMTs low radioactivity)sE/E = 3% at 3 MeV • g and neutron shield: Iron shield (18 cm) + water shield + wood shield + parafin • magnetic field B=25 G • all materials low radioactivity(total activity in 208Tl and 214Bi  300 Bq) 1 sectorof NEMO3

  5. Cathodic rings Wire chamber PMTs Calibration tube scintillators bb isotope foils

  6. AUGUST 2001 June 2002 : tests runs February 2003 :beginning of data taking

  7. wood coil Iron shield Water tank

  8. Sources preparation

  9. Sources bb (thickness ~ 60 mg/cm2) bb(2n) Bkg 100Mo (6.9 kg) 82Se (0.93 kg) Qbb = 3034 keV Qbb = 2995 keV Sources in NEMO-3 detector

  10. Expected background and sensitivity 5 years of data Energy window: [2.8-3.2] MeV Efficiciency bb0n = 14% External and neutron background negligeable 1 kg of 82Se 7 kg of 100Mo Source contamination:A(214Bi) < 0.3 mBq/kg A(208Tl) < 0.02 mBq/kg Internal background:214Bi< 0.04evts/y/kg 208Tl < 0.04evts/y/kg bb(2n) 0.11evts/y/kg Source contamination:A(214Bi) =1.20.5 mBq/kg (measured) A(208Tl) = 0.40.1 mBq/kg Internal background:bb(2n) 0.01 evts/y/kg Hot spots: Pollution rejected Total Bkg < 1.4 event/year T1/2(0n) > 8.1024 y <mn> < 0.1 – 0.3 eV Bkg ~0 event/year T1/2(0n) > 1.5.1024 y <mn> < 0.6 – 1.2 eV

  11. NEMO-3 Preliminary Results • Performance of the detector • bb2n analysis for 100Mo, 82Se, 150Nd • Background analysis for bb0n search

  12. Data Tacking October 1st 2003 161 days of data tacking ~ 75 % efficiency Trigger: 1 PM > 150 keV 3 Geiger hits (2 neighbour layers + 1) Counting rate = 7.5 Hz Proportion of types of events in raw data: Days of data collecting / month Efficiency of data collecting / month

  13. Tracking Detector Performances • 0.5 % Geiger cells OFF • 97.5 % Geiger cells with 2 cathodic signals • Longitudinal propagation of Geiger plasma: • Efficiency > 93% for 90% of Geiger cells RAW DATA PROCESSED DATA

  14. Transversal and Longitudinal Resolution on the Vertex 207Bi sources at 3 well known positions in each sector (emission of two e- conversion at  1 and 0.5 MeV) 1 e- channel at 1 Mev: s (1 MeV) = 0.2 cm s// (1 MeV) = 0.7 cm (Z=0) 2e- channel (1 MeV+ 0.5 MeV) s (1 MeV) = 0.6 cm s// (1 MeV) = 1.8 cm (Z=0)

  15. 976 keV 207Bi FWHM = 135 keV 90Sr 482 keV End point 2,28 MeV Performances of the calorimeter Tube in each sector where calibration sources are introduced (3 positions) 3 electron energies : 486 keV and 976 keV with207Bi, and 2.28 MeV with90Sr At 1 MeV (Qbb3 MeV for 100Mo and 82Se):

  16. bb2n EVENT OBSERVED BY NEMO-3… E1+E2= 2088 keV (Dt)mes –(Dt)theo = 0.22 ns (Dvertex) = 2.1 mm (Dvertex)// = 5.7 mm bb2n event

  17. 100Mo 22 preliminary results (14 Feb. 2003 – 30 Sep. 2003) NEMO 3 Background substracted 22 Monte Carlo 160 days 75535 events S/B = 40 S/B(> 1 MeV)  100 T1/2 = 7.8 ± 0.09 (stat) ± 0.09 (syst)  1018 y

  18. HSD, higher levels contribute to the decay 1+ SSD, 1+ level dominates in the decay (Abad et al., 1984, Ann. Fis. A 80, 9) 100Tc 0+ 100Mo 0+ 100Mo 22 Single Energy Distribution Calculations for 100Mo: (Simkovic, J. Phys. G, 27,2233, 2001) Effect in one electron spectrum

  19. 100Mo 22 angular distribution Background substracted NEMO 3 22 Monte Carlo

  20. 82Se 22 preliminary results (14 Feb. 2003 – 30 Sep. 2003) Background substracted 22 Monte Carlo 3834 hours 1100 events S/B = 4.2 Contaminated with low energy -emitters Cuts: E > 300 keV Cos () < 0.7 T1/2 = 9.52 ± 0.25 (stat) ± 0.9 (syst)  1019 y

  21. 150Nd 22 preliminary results (June 2002 – 30 Sep. 2003) Background substracted 22 Monte Carlo 3834 hours 400 events S/B = 4.2 T1/2 = 7.5 ± 0.3 (stat) ± 0.7 (syst)  1018 y

  22. Origin of Background at high energy Two natural isotopes which have the greatest Qb values > 3 MeV: 214Bi : Qb  3.27 MeV 208Tl : Qb  4.99 MeV Design NEMO-3 detector for 10 kg: 214Bi in source foils < 0.3 mBq/kg 208Tl in source foils < 0.02 mBq/kg Total activity of the detector (200 tons)  300 Bq In the Modane Underground Laboratory: Fast neutron flux ( 1 MeV): 3.5 ± 1.5 10-6 n.cm-2s-1 Thermal neutron flux (~0.025 eV): 1.6 ± 0.1 10-6 n.cm-2s-1

  23. How NEMO-3 tags the background • Electron • Gamma : 50% efficiency at 1 MeV Energy Threshold = 30 keV • Time of Flight : Time Resolution  250 ps at 1 MeV • e+/e- separation with a magnetic field of 25 G 3% confusion at 1 MeV • Delayed tracks (<700 ms) to tag delayed a from Bi207 214Bi  214Po (164 ms)  210Pb

  24. channel e- (g) a with T1/2 (a) = 164 ms (214Bi - 214Po -210Pb) 214Bi Measurement of the sources of background channels e-g ’s with Eg= 2.6 MeV 212Bi 212Po e- (g) a T1/2(a)=300 ns 208Tl neutrons, external gammas e- crossing, e+e-, e-e- > 4 MeV

  25. BACKGROUND EVENTS OBSERVED BY NEMO-3… Electron + a delay track (164 ms) 214Bi 214Po 210Pb Electron crossing > 4 MeV Neutron capture  Electron – positron pair B rejection Electron + N g’s 208Tl (Eg = 2.6 MeV)

  26. Search for 208Tl background in the foils look for eg, e2g, e3g events coming from the foil 3800 h of data analysed 14 Feb. 2003 – 30 Sep. 2003 Tl cuts:E1 > 400 keV E2 > 1900 keV E > 200 keV MC:(Mo) = 0.16% 3.4 Rn events (3800 h.) for 20 sectors VERY PRELIMINARY Good agreement with the HPGe measurements

  27. Neutron and High-Energy gamma Background look for e-e- events > 4 MeV coming from the foil Only 1 bb0n-like event > 4 MeV detected after 160 days of data tacking ! (14 Feb. 2003 – 30 Sep. 2003) Run 2058 event 345966 26 March 2003 130Te source (sector 19) E1+E2 = 4448 keV

  28. Radon in NEMO-3 222Rn • Two different measurements of radon in the NEMO-3 gas: • Radon detector: • sensitivity: 1 count/day for 1 mBq/m3 • Radon measurement  20 mBq/m3 • (1e- + 1 a) channel in the NEMO-3 data: • Able to measure Radon every half day • Radon measurement  30 mBq/m3 214Po 218Po b a 164 ms 214Bi 210Pb 214Pb ~ a fewbb0n-likeevents due to radon, expected in 1 year !!! TOO HIGH !!! • A free Radon Tent surrounding the NEMO-3 detector in construction: • February 2004: 200 kg Charcoal • Factor ~ 8 for Radon purification • Spring 2004: Full Radon purification system • Factor ~ 100

  29. Run 2220, event 136.604, May 11th 2003 E1+E2= 2880 keV a bb0n-like event due to Radon from the gas a track (delay = 70 ms) 214Po 210Pb • 214Bi 214Po • decay IN THE GAS

  30. Free-Radon Purification System Today : A(222Rn) in the LSM ~10 Bq/m3 Fall 2003 : Tent surrounding the detector A(222Rn) ~ Bq/m3 Spring 2004 : Radon-free Gas Facory A(222Rn) ~ 0.2 Bq/m3 150 m3/h

  31. Sensitivity of NEMO3 to measure sources of background Design NEMO3 for 10 kg: 208 Tl in source foils < 0.02 mBq/kg 214 Bi in source foils < 0.3 mBq/kg neutron flux < 10-8n cm-2 s-1 Sensitivity NEMO3after 2 years of data: 208 Tl in source foils< 2 mBq/kg channel eg ’s (Eg = 2.6 MeV) 212 Bi  212 Po e(g)a (300 ns) 214 Bi in source foils< 2 mBq/kg measured by channel e (g) +a ( 214 Bi  214 Po  210 Pb; T1/2 = 164 ms ) neutrons< 10-9 n cm-2 s-1 measured by e- crossing > 4 MeV Sensitivity to 100 kg of isotopes

  32. Future for a NEMO Detector Tracking-Calorimeter Technique

  33. QD NEMO-3 IH QD NEMO-3 IH QD NEMO-3 IH Expected values of <mn> from neutrinos oscillations parameters Pascoli and Petcov, hep-ph/0310003 (best fit natm + nsol ) Quasi-Degenerate (QD): <mn> > 0.6 eV ~ Inverted Hierarchie (IH): 0.015 eV < <mn> < 0.6 eV ~ ~ Normal Hierarchie (NH): <mn> < 5. 10-3 eV ~ Next Generation of NEMO detector « detect » 1 gold event/year with <mn> ~ 20 meV

  34. ln2 . N . e . M Nbb0n / year = • M =k  100 kg of 100Mo or 82Se • e = 0.5 • Background = 0.1 event / year • 1 bb0n Gold event detected / year mn = 20 – 60 meV 0n A . T1/2 (y) 0n T1/2 = 2  k 1026 years Future of NEMO Number of bb0n event detected / year: N : Avogadro A : atomic mass M : mass (g) of bb enrich. Isotope e : detection efficiency Goal of a next NEMO detector: Real measurement with 1 GOLD EVENT / YEAR

  35. Future of NEMO • 3-4-5 December 2003: 1st meeting for Future of NEMO • Start working groups to prepare a design proposal for a future NEMO detector • Advantage of a Calo-Tracking approach: • Can measure several isotopes • Tag and measure all backgounds : zero background experiment • May detect « Gold events » • Start with realistic 100 kg isotope module… • could be extended to 1 ton with several modules) • Working groups: • R&D Calorimeter • R&D Tracking • Sources Enrichment (100Mo, 82Se, 150Nd…) • Purification sources • Simulation • Main challenges: • Energy resolution • Efficiency • Sources (enrichment, purification)

  36. FWHM (bb0n ray at 3 MeV)  350 keV one bb2n event/year expected in the bb0n energy window NEMO-3 (7 kg): • s2 (bb0n ray) = s2 (Calorimeter) + s2 (dE/dX in foil) + s2 (dE/dX in tracking) • CALORIMETER: separate e-/g measurement to improve e- energy resolution • (NEMO-3 ~ 15% at 1 MeV) • electron:Silicon (Li) detector (~ 5 mm, noise ~ 20-30 keV at normal To) • Very good thin scintillator (~ 2 cm) • gamma: thicker scintillators (100% efficiency instead of 50%) • SOURCES: Decrease the energy losses in the foil • (NEMO-3 ~ 50-80 g/cm2, 60 mm: <DE> ~150 keV) • Active sources (ex:2 foils 20 mm + counters)  internal Background rejection • TRACKING: • Similar Geiger drift wire chamber • TPC in He (Japan group) e- b- g 208Tl internal bkg b- b- ENERGY RESOLUTION IS ONE OF THE MAIN CHALLENGE Goal: < 0.1 bb2n event/year in the bb0n energy window

  37. ILIAS European funding for bb0n research IN2P3 (5 years) NEMO people involved in ILIAS (5 years) • JRA1: low bkg. techn. for Deep Underground Laboratories • Links LSM and Boulby • Develop. Ultra Low Bkg. Facility: Big effort on Germanium • Radon factory 300 kEuros • JRA2: R&D for next detectors • R&D for calorimeter (silicon, scintillators…) • 82Se 2 kg production, purification and source making (2004-2005) • 150Nd enrichment study 300 kEuros • N4: next generation of bb0n detectors • NEMO-Next working groups and Proposal 60 kEuros

  38. New members already interested: USA (Texas University), UK (UCL), Japan (KEK) NOUVEAUX COLLABORATEURS SONT LES BIENVENUS

  39. CONCLUSIONS • NEMO-3 Detector running since 14 Feb. 2003 Data tacking efficiency ~75% • Performance of the detector has been reached ! • 2b2n preliminary results for 100Mo, 82Se and 150Nd already more than 75.000 2b2n events collected • Background study for 2b0n search: • 208Tl (e- Ng channel) : good agreement with HPGe measurements • Neutrons and High-energy g: only 1 bb0n-like event > 4 MeV ! • Radon: 20-30 mBq/m3 inside the detector • a few bb0n-like events/year expected Too high ! • Free radon purification system under construction Radon/8 in Feb. 2004 Radon/50 in Spring 2004 • Future of NEMO: First meeting 3-5 december 2003 start working groups to prepare a design proposal for a next detector Goal (dream ?) for Next NEMO: be able to « detect » 1 gold event/year with <mn> ~ 20 meV

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