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Recent Results of the NEMO 3 Experiment

Recent Results of the NEMO 3 Experiment. Ladislav VÁLA Czech Technical University in Prague. NOW2006, 9 th – 16 th September 2006, Conca Specchiulla, Italy. Outline. Double beta decay NEMO 3 description NEMO 3 results (2 nbb & 0 nbb & 0 ncbb ) Conclusion. Introduction.

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Recent Results of the NEMO 3 Experiment

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  1. Recent Results of the NEMO 3 Experiment Ladislav VÁLA Czech Technical University in Prague NOW2006, 9th – 16th September 2006, Conca Specchiulla, Italy

  2. Outline Double beta decay NEMO 3 description NEMO 3 results (2nbb & 0nbb & 0ncbb) Conclusion

  3. Introduction

  4. Two-neutrino bb decay (2nbb): (A,Z)→(A,Z+2) + 2 e- + 2ne Neutrinoless bb decay (0nbb): (A,Z)→(A,Z+2) + 2 e- W- • 0nbb & 0ncbb: DL = 2 process • Majorana neutrino n≡n and effective mass mn • Light neutrino exchange → mn • Right-handed (V+A) current in weak interaction → mn, l, h) • Majoron emission → gM • SUSY particle exchange → l111,l113,l 131, bb with Majoron emission (0ncbb): (A,Z)→(A,Z+2) + 2 e- + c p neR h n e- neL h nM 0nbb e- W- n p Double beta decay

  5. Two electron energy spectrum Experimental signature: 2 electrons E1 +E2 = Qbb arbitrary units (Qbb ~ MeV) Neutrinoless Double Beta Decay G0n = (T1/2)-1 = G0n(Qbb5,Z)|M0n|2mn2 G0n– phase space factor M – nuclear matrix element mn – effective neutrino mass mn = |Sj |Uej|2 eiaj mj |

  6. NEMO 3 description

  7. NEMO 3 Collaboration CEN Bordeaux-Gradignan, France Charles University, Prague, Czech Republic Czech Technical University, Prague, Czech Republic INEEL Idaho Falls, USA INR Moscow, Russia IReS Strasbourg, France ITEP Moscow, Russia JINR Dubna, Russia Jyväskylä University, Finland LAL Orsay, France LSCE Gif-sur-Yvette, France LPC Caen, France University of Manchester, United Kingdom Mount Holyoke College, USA Kurchatov Institute, Moscow, Russia Saga University, Japan University College London, United Kingdom

  8. 20 sectors 3 m 6 m B (25 G) 4 m 6 m NEMO 3 detector Detector located in the Fréjus Underground Laboratory, France (4800 m.w.e.) Source: 10 kg of  isotopes, cylindrical, S = 20 m2, foils ~ 60mg/cm2 Tracking detector: drift wire chamber operating in Geiger mode (6180 cells) gas = 94% He + 4% ethyl alcohol + 1% Ar + 0.1% H2O Calorimeter: 1940 plastic scintillators coupled to low radioactivity PMTs Magnetic field: 25 Gauss Gamma shield: pure iron (18 cm layer) Neutron shield: borated water (ext. wall, 30 cm layer) & wood (top and bottom, 40 cm layer) identification of e–, e+, g and a-particles

  9. 100Mo6.914 kg Qbb= 3034 keV & 82Se0.932 kg Qbb = 2995 keV External background measurement 2nbb decay measurement 0nbb decay search NEMO 3 sources 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 natTe491 g Cu621 g

  10. Transverse view Longitudinal view Run Number: 2040 Event Number: 9732 Date: 2003-03-20 Vertex of the e-e- emission 100Mo foils Scintillator + PMT Vertex of the e-e- emission Deposited energy: E1 + E2= 2088 keV Internal hypothesis: (Dt)mes – (Dt)theo = 0.22 ns Common vertex: (D vertex) = 2.1 mm (D vertex)// = 5.7 mm bb event from data

  11. External background 208Tl (PMTs) Measured with (e-g) external events ~ 10-3 0nbb-like events y-1·kg -1 with 2.8<E1+ E2<3.2 MeV External neutrons and high energy g’s Measured with (e-e+)int events with E1+E2 > 4 MeV  0.02 0nbb-like events y-1·kg -1 with 2.8<E1+ E2<3.2 MeV 208Tl impurities inside the foils Measured with (e-2g), (e-3g) events coming from the foil ~ 0.1 0nbb-like events y-1·kg -1 with 2.8<E1+ E2<3.2 MeV 100Mo 2nbb decayT1/2 = 7.1 × 1018 y ~ 0.3 0nbb-like events y-1·kg -1 with 2.8<E1+ E2<3.2 MeV Background measurement NEMO 3 can measure each component of its background!

  12. 222Rn (3.8 days) Radon in the NEMO 3 gas of the wire chamber a 214Bi →214Po (164 ms) →210Pb b- Due to a tiny diffusion of the radon of the laboratory inside the detector: A(Rn) in the lab ~15 Bq/m3 214Po 218Po b a 164 ms 214Bi Two independent measurements of radon in the NEMO 3 gas b- 210Pb 214Pb Decay in the gas Radon detector at the input/output of the NEMO 3 gas (1e- + 1a) channel in the NEMO 3 data delayed a Good agreement between the two measurements A(Rn) inside NEMO 3  20-30 mBq/m3 (Phase I) ~ 1 0nbb-like event/y/kg with 2.8 < E1+E2 < 3.2 MeV Radon was the dominant background for the 0nbb search in the NEMO 3 Phase I data !!! Radon background

  13. Radon trapping facility February 2003 – September 2004: Phase I (radon background in data) Since October 2004: Phase II (radon level reduced by a factor of 10) Start-up: October 4th 2004 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 NEMO 3 tent: factor of 100 – 300 inside NEMO 3: factor of 10 A(222Rn)  2 mBq/m3 Radon background is negligible today! 0.015 Bq/m3

  14. Radon trapping facility dryer charcoal columns chilling unit buffer compressor

  15. NEMO 3 results

  16. 219 000 events 6914 g 389 days S/B = 40 219 000 events 6914 g 389 days S/B = 40 Data Data 2b MC simulation 2b MC simulation Background subtracted Background subtracted cos(ee) E1 + E2 (MeV) 100Mo: 2nbb decay Sum Energy Spectrum Angular Distribution T1/2 = [ 7.11 ± 0.02 (stat) ± 0.54 (syst) ]  1018 y Phys. Rev. Lett. 95 (2005) 182302

  17. Single electron spectrum different between SSD and HSD Šimkovic et al., J. Phys.G27 (2001) 2233. HSD, higher levels contribute to the decay Esingle (keV) 1+ HSD 100Tc SSD, 1+ level dominates in the decay Abad et al., Ann. Fis. A 80 (1984) 9. 0+ • Data • Data SSD 100Mo 2b HSD MC simul. 2b HSD MC simul. Background subtracted Background subtracted 2/ndf = 139./36 2/ndf = 40.7/36 Esingle (keV) Single electron energy distribution of the 2bb decay of 100Mo in favor of Single State Dominance (SSD) model Esingle (keV)

  18. 0+ 100Mo 3034 keV 41+ (1227 keV) g2 01+ (1130 keV) 21+ (540 keV) 22+ (1362 keV) g1 0+ (g.s.) 100Ru 100Mo: bb decay to exc. states 334.3 days of data (Phase I) 2nbb decay to the 01+ state: S/B = 3.0 T1/2 =[ 5.7+1.3-0.9(stat) ± 0.8(syst)]1020 y 0nbb decay to the 01+ state: T1/2 > 8.9  1022 y@ 90 % C.L. 2nbb decay to the 21+ state: T1/2 > 1.1  1021 y @ 90 % C.L. 0nbb decay to the 21+ state: T1/2 > 1.6  1023 y@ 90 % C.L. To be published soon, submitted to Nucl. Phys. A Clear topology: 01+: 2e- + 2g in time & energy and TOF cuts 21+: 2e- + 1g in time & energy and TOF cuts

  19. 693 days of data Phase I + Phase II 100Mo: 0nbb decay Energy window: 2.78 MeV < Eee < 3.20 MeV 14 events observed, 13.4 events expected 7.9 events excluded at 90% C.L. V-A: T1/2 > 5.8 × 1023 y @ 90% C.L. mn < (0.6 – 0.9) eV [1-3], < (2.1 – 2.7) eV [4] V+A: T1/2 > 3.2 × 1023 y @ 90% C.L. l < 1.6 × 10-6 [5] [1] F.Šimkovic et al.,Phys.Rev. C 60 (1999) 055502. [2] S.Stoica et al., Nucl.Phys. A 694 (2001) 269. [3] O.Civitarese et al., Nucl.Phys. A 729 (2003) 867. [4] V.A.Rodin et al., Nucl.Phys. A 766 (2006) 107. [5] J.Suhonen et al., Nucl.Phys. A 700 (2002) 649. NME:

  20. Sum Energy Spectrum 2750 events 932 g 389 days S/B = 4 Data 2b MC simulation Background subtracted E1 + E2 (MeV) 82Se: 2nbb decay T1/2 = [ 9.6 ± 0.3 (stat) ± 1.0 (syst) ]  1019 y Phys. Rev. Lett. 95 (2005) 182302

  21. 693 days of data Phase I + Phase II 82Se: 0nbb decay Energy window: 2.62 MeV < Eee < 3.20 MeV 7 events observed, 6.4 events expected 6.2 events excluded at 90% C.L. V-A: T1/2 > 2.1 × 1023 y @ 90% C.L. mn < (1.2 – 2.5) eV [1-3], < (2.6 – 3.2) eV [4] V+A: T1/2 > 1.2 × 1023 y @ 90% C.L. l < (2.8 – 3.0) × 10-6 [6] [1] F.Šimkovic et al.,Phys.Rev. C 60 (1999) 055502. [2] S.Stoica et al., Nucl.Phys. A 694 (2001) 269. [3] O.Civitarese et al., Nucl.Phys. A 729 (2003) 867. [4] V.A.Rodin et al., Nucl.Phys. A 766 (2006) 107. [6] M.Aunola et al., Nucl.Phys. A 463 (1998) 207. NME:

  22. 150Nd 96Zr 2348 evts 405 g 365.4 days S/B = 7.6 818 events 37 g 365.4 days S/B = 2.4 127 events5.3 g 365.4 days S/B = 0.9 116Cd E1+E2 (MeV) E1+E2 (MeV) E1+E2 (MeV) Data Data Data 2nbb simul. 2nbb simul. 2nbb simul. 116Cd, 150Nd, 96Zr: 2nbb decay Background subtracted Preliminary results: 116Cd:T1/2 = [ 2.8 ± 0.1 (stat) ± 0.3 (syst) ]  1019 y (SSD) 150Nd: T1/2 = [ 9.7 ± 0.7 (stat) ± 1.0 (syst) ]  1018 y 96Zr:T1/2 = [ 2.0 ± 0.3 (stat) ± 0.2 (syst) ]  1019 y

  23. 48Ca E1+E2 (MeV) 48Ca: 2nbb decay 40 events7.0 g 466.7 days S/B = 15.7 Phase I + Phase II data Ee > 0.7 MeV & cos(ee) < 0 Very small background! Preliminary result: 48Ca:T1/2 = [ 3.9 ± 0.7 (stat) ± 0.6 (syst) ]  1019 y

  24. 100Mo: T1/2 > 2.7 × 1022 y @ 90% C.L. gee < (0.5 – 1.9) × 10-4 82Se: T1/2 > 1.5 × 1022 y @ 90% C.L. gee < (0.7 – 1.7) × 10-4 Nucl. Phys. A 765 (2006) 483. [1] F.Šimkovic et al.,Phys.Rev. C 60 (1999) 055502. [2] S.Stoica and H.V. Klapdor-Kleingrothaus, Nucl.Phys. A 694 (2001) 269. [3] O.Civitarese and J.Suhonen, Nucl.Phys. A 729 (2003) 867. [4] V.A.Rodin et al., Nucl.Phys. A 766 (2006) 107. NME: 0nbb decay Netrinoless bb decay with Majoron emission (A,Z) → (A,Z+2) + 2e- + c0 334.3 days of data (Phase I)

  25. Conclusion

  26. Conclusion No signal seen for 0nbb decay Improved limits: 100Mo: T1/2 > 5.8 × 1023 y, mn < (0.6 – 2.7) eV 82Se: T1/2 > 2.1 × 1023 y, mn < (1.2 – 3.2) eV Improved limits for 0ncbb decay of 100Mo and 82Se 2nbb decay of 100Mo and 82Se measured with high statistics Preliminary results for other isotopes New measurement and T1/2 limits for bb decay of 100Mo to excited states Analysis of Phase II data in progress

  27. Spare Slides About SuperNEMO

  28. SuperNEMO Ladislav VÁLA Czech Technical University in Prague NOW2006, 9th – 16th September 2006, Conca Specchiulla, Italy

  29. SuperNEMO Project • extension of the NEMO 3 technique • 100–200 kg of isotopes, thin source between tracking volumes, surrounded by calorimeter. • sensitivity T1/2(0nbb) > 1026 y, mn < 50 meV • main improvements needed: • energy resolution (FWHM @ 3 MeV = 4%) • detection efficiency (factor of 2) • source radio purity (factor of 10) • background rejection methods

  30. Japan U. Saga U. Osaka Marocco Fes U. USA MHC INL (U. Texas) UK UC London U Manchester IC London Finland U. Jyväskylä Russia JINR Dubna INR Moscow ITEP Moscow Kurchatov Institute Ukraine INR Kiev ISMA Kharkov France CEN Bordeaux IReS Strasbourg LAL Orsay LPC Caen LSCE Gif/Yvette Slovakia U. Bratislava Spain U. Valencia U. Zarogoza U. Autonoma Barcelona Czech Republic Charles U. Prague CTU Prague SuperNEMO Collaboration NEMO collaboration + new labs ~ 60 physicists, 11 countries, 27 laboratories

  31. 3 m Number of modules = 20 For each module: Calorimeter : 300 to 1000 PMT’s (depending on the final design) Resolution (FWHM) at 3 MeV = 4% Tracking : drift chamber (3000 cells in Geiger mode) Magnetic field : 25 gauss 14 m Source foil: 5 kg of enriched 150Nd or 82Se Water shield: 2kT of water for 20 modules (0 ) ~ 30 % Possible Design

  32. 1 Goal : T1/2  1026 y m 50 meV 2 2 = GMm T  82Se Phase space factor G0 = 1.08 x 10-25 y-1eV-2 Q = 2.995 MeV 214Bi < 10 Bq/kg 208Tl < 2 Bq/kg Rn < 2 Bq/m3 Radiopurity requirements for the  source T2 = 9 x 1019 y Expected background from 2nbb = 1.4 evt/500kg.y in 200 keV (200 keV energy window at Q) Enrichment by ultracentrifugation 150Nd Q = 3.367 MeV Phase space factor G0 = 8.00 x 10-25 y-1eV-2 Radiopurity requirements for the  source 208Tl < 2 Bq/kg T2 = 9 x1018 y  Expected background from 2nbb = 2.2 evt/500kg.y in 200 keV (200 keV energy window at Q) Enrichment by laser bb Sources The best choice for phase space and background

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