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NEMO-3 A search for double beta decay

NEMO-3 A search for double beta decay. Robert L. Flack University College London On behalf of the NEMO-3 collaboration. Overview. NEMO-3 The collaboration. The detector. The sources. Event reconstruction. Radon trapping facility (phase 1 and 2 data). Results Past Latest

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NEMO-3 A search for double beta decay

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  1. NEMO-3A search for double beta decay Robert L. Flack University College London On behalf of the NEMO-3 collaboration NEMO-3 Neutrino08

  2. Overview • NEMO-3 • The collaboration. • The detector. • The sources. • Event reconstruction. • Radon trapping facility (phase 1 and 2 data). • Results • Past • Latest • The future – SuperNEMO • Comparison with NEMO-3. NEMO-3 Neutrino08

  3. NEMO3(NeutrinoEttoreMajoranaObservatory) 60 physicists, 17 institutions NEMO-3 Neutrino08

  4. The NEMO-3 detector 20 sectors B(25 G) 3 m Magnetic field: 25 Gauss Gamma shield: Pure Iron (e = 18 cm) Neutron shield: 30 cm water (ext. wall) 40 cm wood (top and bottom) (since march 2004: water + boron) 4 m Particle ID: e-, e+, g and a Fréjus Underground Laboratory : 4800 m.w.e. Source: 10 kg of  isotopes cylindrical, S = 20 m2, e ~ 60 mg/cm2 Tracking detector: drift wire chamber operating in Geiger mode (6180 cells) Gas: He + 4% ethyl alcohol + 1% Ar + 0.1% H2O Calorimeter: 1940 plastic scintillators coupled to low radioactivity PMTs NEMO-3 Neutrino08

  5. bb2n measurement bb0nsearch bbdecay isotopes in NEMO-3 detector 116Cd405 g Qbb = 2805 keV 96Zr 9.4 g Qbb = 3350 keV 150Nd 37.0 g Qbb = 3367 keV 48Ca 7.0 g Qbb = 4272 keV 130Te454 g Qbb = 2529 keV External bkg measurement natTe491 g 100Mo6.914 kg Qbb = 3034 keV 82Se0.932 kg Qbb = 2995 keV Cu621 g (Enriched isotopes produced by centrifugation in Russia) NEMO-3 Neutrino08

  6. Vertex of the e-e- emission Source foils Scintillator + PMT Vertex of the e-e- emission Event reconstruction Transverse view Longitudinal view Observables of the final state • Trajectories of the 2 electrons • Energies of the 2 electrons • Time of flight • Curvature of the tracks in a B-field (+ or -). NEMO-3 Neutrino08

  7. Radon trapping facility Radon trapping facility (First developed for SuperKamiokande) Phase I : February 2003 – September 2004 (radon background in data) ~ 1 0nbb-like event/y/kg with 2.8 < E1+E2 < 3.2 MeV Phase II : since October 2004 (radon level reduced by a factor of 6) 1 ton of charcoal @ –50oC, 9 bars air flux = 150 m3/h Input: A(222Rn) 15 Bq/m3 Output: A(222Rn) < 15 mBq/m3 !!! reduction factor of 1000 Inside the NEMO 3 tent: factor of 100 – 300 Inside NEMO 3: almost factor of 10 A(222Rn)  6 mBq/m3 NEMO-3 Neutrino08

  8. 12000 10000 8000 6000 4000 2000 0 Number of events • Data-bkg = sig • Data-bkg = sig 22 Monte Carlo 22 Monte Carlo Background Background 100Mo 2results Angular distribution Sum energy spectrum 219 000 events 6914 g 389 days S/B = 40 219 000 events 6914 g 389 days S/B = 40 12000 10000 8000 6000 4000 2000 0 NEMO-3 NEMO-3 100Mo 100Mo Number of events/0.05 MeV Cos() E1 + E2 (MeV) T1/2(2nbb) = 7.11 ± 0.02 (stat) ± 0.54 (syst)  1018 years Phase 1: Feb. 2003 – Dec. 2004 “High Radon” Now have in excess of 0.5M events and will update later this year. Phys. Rev. Lett. 95 182302 (2005) NEMO-3 Neutrino08

  9. 2n results with other nuclei NEMO-3 932 g 389 days 2750 events S/B = 4 NEMO-3 454 g 534 days 109 events S/B = 0.25 82Se 130Te Preliminary: Result for Phase 1 and 2 data. 130Te: T1/2 = [7.6 ± 1.5 (stat) ± 0.8 (syst)]  1020 y Results for Phase I data. Additional statistics are being analysed and to be published soon. 82Se: T1/2 = [9.6 ± 0.3 (stat) ± 1.0 (syst) ]  1019 y 116Cd: T1/2 = [2.8 ± 0.1 (stat) ± 0.3 (syst) ]  1019 y 2nbbis important:1) Experimental input to NME calculation 2) Ultimate background for0nbb NEMO-3 Neutrino08

  10. New result: 48Ca bb High bkgs here due to contamination with 90Sr. Cut at 1.5 MeV NEMO-3 NEMO-3 Cut at 0 133 events S/B 6.76 948 days 7g E1 + E2 (MeV) Preliminary results: T1/2 (2nbb) = [4.4 +0.5-0.4 (stat) ± 0.4 (syst)] x 1019 y T1/2 (0) >1.3 x1022 y (90% C.L) <mn> < 29.6 eV (90%CL), Eff. 22% refs: E Caurrier et al., Phys. Rev. Lett. 100 (2008) 052503 (NME) NEMO-3 Neutrino08

  11. New result: 96Zr 2nbb NEMO-3 NEMO-3 925 days S/B 1.01 9.41g Preliminary result: 96Zr:T1/2 (2νββ)= [2.3 ± 0.2(stat) ± 0.3(syst) ]  1019 y T1/2 (2νββ)= 8.6  1021 y (90% C.L) <mn> < 7.4 - 20.1 eV (90%CL), Eff. 19% Refs for NME : Simkovic, et al., Phys. Rev. C 77 (2008) 045503 Kortelainen and Suhonen,Phys. Rev. C 76 (2007) 024315 NEMO-3 Neutrino08

  12. Recent result: 150Nd 2nbb (Moriond) 37g Preliminary results: 150Nd: T1/2 (2νββ) = [9.20 +0.25-0.22 (stat) ± 0.62 (syst)] x 1018 y T1/2 (0νββ) = 1.45 x 1022 y (90% C.L.) <mn> < 3.7 - 5.1 eV (90%CL), Eff. 19% Ref for NME : V. A. Rodin et al., Nucl. Phys. A 766 (2006)107 NEMO-3 Neutrino08

  13. 693 days of data Phase I + Phase II 0nbbof 100Mo and 82Se (To be updated) Data until spring 2006 693 days of data Phase I + Phase II NEMO-3 NEMO-3 82Se 100Mo T1/2 > 5.8 × 1023 y @ 90% C.L. mn < (0.8 – 1.3) eV [1-3] T1/2 > 2.1 × 1023 y @ 90% C.L. mn < (1.4 – 2.2) eV [1-3] [1] M.Kortelainen and J.Suhonen, Phys.Rev. C 75 (2007) 051303(R). [2] M.Kortelainen and J.Suhonen, Phys.Rev. C 76 (2007) 024315. [3] V.A.Rodin et al., Nucl.Phys. A 793 (2007) 213. NME: NEMO-3 Neutrino08

  14. SuperNEMO NEMO-3 isotope 82Se - baseline (150Nd if it can be enriched) 100Mo isotope massM 100-200 kg 7 kg 208Tl mBq/kg if 82Se: 214Bi  10 mBq/kg 208Tl: < 20 mBq/kg 214Bi: < 300 mBq/kg internal contaminations 208Tl and 214Bi in the bb foil energy resolution (FWHM) 8% @ 3MeV 4%@ 3 MeV T1/2(0nbb) > 2 x 1024 y <mn> < 0.3 – 0.9 eV T1/2(0nbb) > 1026 y <mn> < 0.04 - 0.11 eV From NEMO-3 to SuperNEMO NA Me Tobs T1/2 (bb0n) > ln 2   A N90 18 % efficiency  ~ 30 % See SuperNEMO poster NEMO-3 Neutrino08

  15. Summary • NEMO’s Tracking + Calorimetry approach is unique • Good rejection of backgrounds • Choice of isotopes • Reconstruction of kinematics • NEMO3 is taking data • 2nbb factory: precise life-time measurements for 7 isotopes (out of 9 main candidates). • New results for 48Ca and 96Zr. • Data taking until end 2010: 340-590 meV. • SuperNEMO: 3 year Design Study addresses most critical issue • Based on design study results full proposal for 100+ kg detector in 2009. • 82Se – baseline, 150Nd possible. • First module 2010/11. • All 20 modules ~2013. • Target sensitivity: 50-100 meV by 2016 NEMO-3 Neutrino08

  16. Backup slides NEMO-3 Neutrino08

  17. Schedule Summary 2010 2011 2007 2008 2009 2012 2013 BiPo construction 2014 NEMO3 Running SuperNEMO Design Study BiPo1 Canfranc/LSM BiPo installation BiPo running @ Canfranc SuperNEMO 1st module construction Preparation of new LSM site construction of 20 modules 1-5 SuperNEMO modules running at Canfranc Running full detector in 2014 Target sensitivity (0.05-0.1 eV) in 2016 SuperNEMO modules installation at new LSM NEMO-3 Neutrino08

  18. Choice of Isotope • Criteria of choice: • High Qbb value • Phase space G0n • 2nbb half-life • natural abundance • enrichment possibilities. Purification of 4kg of 82Se underway (INL, US). Enrichment of 150Nd possible. 82Se obtained by centrifugation. Impossible for 150Nd, only laser enrichment. NEMO-3 Neutrino08

  19. ββdecay is about background suppression Background. Natural radioactivity: T1/2(238U, 232Th) ~ 1010 yr T1/2(0nbb) > 1025 yr 238U and 232Th produce 214Bi (Qb = 3.27 MeV) and 208Tl(Qb = 4.99 MeV) Radon! Cosmogenic activitity Underground is a must Due to tracking, for SuperNEMO the main focus is on source (foil) purity. Must be super-duper-ultra low < 10 mBq/kg! (For reference humans 10-100 Bq/kg typical materials ~ 1Bq/kg) But how to measure these levels?! NEMO-3 Neutrino08

  20. Choice of site • Canfranc • 2500 m.w.e • LS Modane • 4800 m.w.e • Boulby • 2800 m.w.e Boulby Canfranc NEMO-3 Neutrino08

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