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NEMO3 A search for double beta decay Robert L. Flack University College London On behalf of the NEMO3 collaboration 28 May 2008 NEMO3 Neutrino08 1 Overview NEMO3 The collaboration. The detector, sources. event


  1. NEMO�3 A search for double beta decay Robert L. Flack University College London On behalf of the NEMO�3 collaboration 28 May 2008 NEMO�3 Neutrino08 1

  2. Overview � NEMO�3 � The collaboration. � The detector, sources. event reconstruction. � Radon trapping facility (phase 1 and 2 data). � Results � Past � Latest � The future – SuperNEMO � Comparison with NEMO�3. � Summary 28 May 2008 NEMO�3 Neutrino08 2

  3. NEMO3 ��������� ������ �������� ������������ ������������������������������ 28 May 2008 NEMO�3 Neutrino08 3

  4. The NEMO�3 detector Fréjus Underground Laboratory : 4800 m.w.e. 20 sectors Source : 10 kg of ββ ββ isotopes ββ ββ cylindrical, S = 20 m 2 , d ~ 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 3 m coupled to low radioactivity PMTs Magnetic field: 25 Gauss Gamma shield: Pure Iron (d = 18 cm) Neutron shield: 30 cm water (ext. wall) B (25 G) 40 cm wood (top and bottom) 4 m (since march 2004: water + + + boron) + + , γ γ and α α Particle ID: e − − , e + γ γ α α − − + + 28 May 2008 NEMO�3 Neutrino08 4

  5. ββ decay isotopes in NEMO�3 detector ββ ββ ββ 05 04 ββ2ν measurement ββ2ν ββ2ν ββ2ν 06 03 02 07 116 Cd 405 g � ββ ��%(�'�#�$ 08 01 96 Zr 9.4 g 09 00 � ββ �!!'��#�$ 150 Nd 37.0 g 19 10 � ββ ��!!���#�$ 48 Ca 7.0 g 18 11 � ββ �"%�%�#�$ 17 12 130 Te 454 g 13 16 � ββ �%'%&�#�$ 14 15 External bkg nat Te 491 g measurement 100 Mo 6.914 kg 82 Se 0.932 kg Cu � ββ �!�!"�#�$ 621 g � ββ �%&&'�#�$ ββ0ν search ββ0ν ββ0ν ββ0ν ��������� ��������������������� 28 May 2008 NEMO�3 Neutrino08 5 �������������������������

  6. Event reconstruction ����������� ������������� ���� ���� ���������� ����� − − � − − − − − − ������������ �������� ������������ + = � � � ����� ββ � % ���������� ����� − − � − − − − − − �������� 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 �). 28 May 2008 NEMO�3 Neutrino08 6

  7. Radon trapping facility Radon trapping facility (First developed for SuperKamiokande) Phase I : February 2003 – September 2004 (radon background in data) ~ 1 0ν 0ν 0ν 0νββ ββ ββ ββ �like event/y/kg with 2.8 < E 1 +E 2 < 3.2 MeV Phase II : since October 2004 (radon level reduced by a factor of 6) �� ton of charcoal @ –50 o C, 9 bars air flux = 150 m 3 /h Input: A( 222 Rn) 15 Bq/m 3 Output: A( 222 Rn) < 15 mBq/m 3 !!! reduction factor of 1000 Inside the NEMO 3 tent: factor of 100 – 300 Inside NEMO 3: almost factor of 10 A( 222 Rn) ≈ ≈ ≈ ≈ 6 mBq/m 3 28 May 2008 NEMO�3 Neutrino08 7

  8. 100 Mo 2 ν ν νββ ν ββ ββ results ββ Angular distribution Sum energy spectrum Number of events/0.05 MeV Number of events 12000 12000 219 000 events 219 000 events ������ ������ 6914 g 6914 g ��� �� ��� �� 389 days 389 days 10000 10000 S/B = 40 S/B = 40 8000 8000 � Data�bkg = sig 2 β β β 2 ν β ν ν ν � Data�bkg = sig Monte Carlo 6000 6000 2 β β 2 ν ν β β ν ν Background Monte Carlo Background 4000 4000 2000 2000 0 0 Cos( θ θ θ ) θ E 1 + E 2 (MeV) × 10 18 years × 10 18 years T 1/2 ( 2νββ 2νββ 2νββ ) = 7.11 ± 2νββ ± 0.02 (stat) ± ± ± ± ± ± 0.54 (syst) × × × T 1/2 ( 2νββ 2νββ 2νββ ) = 7.11 ± 2νββ ± 0.02 (stat) ± ± ± ± 0.54 (syst) × ± ± × × )������*�+��,�%��!�� -��,�%��"� ��4����������5������6� ����������� �����!"�#$%�&%��%&&"�� ./�0��1�2��3 �,'�����������2�4�77� ��2����7��������������, 28 May 2008 NEMO�3 Neutrino08 8

  9. 2ν 2ν 2ν 2νββ ββ ββ ββ results with other nuclei 932 g ������ ������ 454 g 389 days 534 days 2750 events 109 events 82 Se 130 Te S/B = 4 S/B = 0.25 Preliminary: Results for Phase I data. Additional statistics are being analysed and to be published soon. Result for Phase 1 and 2 data. 82 Se: 130 Te: × 10 19 y T 1/2 = [9.6 � 0.3 (stat) � 1.0 (syst) ] × × × × 10 20 y T 1/2 = [7.6 ± 1.5 (stat) ± 0.8 (syst)] × × × 116 Cd: × 10 19 y T 1/2 = [2.8 � 0.1 (stat) � 0.3 (syst) ] × × × 2νββ is important: 2νββ 2νββ 2νββ 2νββ 2νββ 2νββ 2νββ is important: 1) Experimental input to NME calculation 1) Experimental input to NME calculation 28 May 2008 NEMO�3 Neutrino08 9 2) Ultimate background for 0νββ 0νββ 0νββ 0νββ 0νββ 0νββ 0νββ 0νββ 2) Ultimate background for

  10. New result: 48 Ca ββ ββ ββ ββ ��������� ������������ ������������������� �� ��� 8�������,'���$ ������ ������ 8������� �!!������� :;<��,�� &"(�2��� �0 � � 9�� % ���$� ± 0.4 (syst)] x 10 19 y �0.4 (stat) ± ± ± Preliminary results: T 1/2 (2 νββ) νββ) = [4.4 +0.5 νββ) νββ) νββ ) >1.3 x10 22 y (90% C.L) <m ν T 1/2 (0 νββ νββ νββ ν > < 29.6 eV (90%CL), Eff. 22% ν ν Refs: E Caurrier et al., Phys. Rev. Lett. 100 (2008) 052503 (NME) 28 May 2008 NEMO�3 Neutrino08 10

  11. New result: 96 Zr 2νββ 2νββ 2νββ 2νββ ������ ������ &%'�2���� :;<��,�� &,"�0 Preliminary result: × 10 19 y T 1/2 (2νββ) = [2.3 ± 0.2(stat) ± 0.3(syst) ] × × × 96 Zr: × 10 21 y (90% C.L) <m ν T 1/2 (0νββ) = 8.6 × × × ν > < 7.4 � 20.1 eV (90%CL), Eff. 19% ν ν Refs for NME : Simkovic, et al., Phys. Rev. C 77 (2008) 045503 Kortelainen and Suhonen, Phys. Rev. C 76 (2007) 024315 28 May 2008 NEMO�3 Neutrino08 11

  12. Recent result: 150 Nd 2νββ ( 2νββ ( 2νββ ( 2νββ ( Moriond ) ) ) ) Mass = 37g ± 0.62 (syst)] x 10 18 y �0.22 (stat) ± ± ± Preliminary results: T 1/2 (2νββ) = [9.20 +0.25 Expected T 1/2 (0νββ) = 1.45 x 10 22 y Observed T 1/2 (0νββ) = 1.8 x 10 22 y (90% C.L.) Eff. 19% <m ν ν > < 1.7 – 2.4 eV (90%CL), QRPA (2007, corrected paper compared to 2006) ν ν deformation not taken into account <m> < 4.8�7.6 eV: pseudo�SU(3) Hirsh (95) deformation taken into account Ref for NME : V. Rodin et al., Nucl. Phys. A 793 (2007) 213 . 28 May 2008 NEMO�3 Neutrino08 12 J.H. Hirsch et al., Nucl. Phys. A 582 (1995) 124.

  13. 0νββ of 100 Mo and 82 Se 0νββ 0νββ 0νββ �=�������2���2� �� ���!��������� Data until spring 2006 �� ���!��������� ������"���������"" ������"���������"" ������ ������ $% �� �## �� T 1/2 > 5.8 × 10 23 y @ 90% C.L. T 1/2 > 2.1 × 10 23 y @ 90% C.L. 〈 m ν 〈 〈 〈 〈 m ν 〉 < (1.4 – 2.2) eV [1�3] 〈 〈 〈 ν 〉 〉 〉 ν 〉 〉 〉 〉 < (0.8 – 1.3) eV [1�3] ν ν ν ν [1] M.Kortelainen and J.Suhonen, Phys.Rev. C 75 (2007) 051303(R). NME: [2] M.Kortelainen and J.Suhonen, Phys.Rev. C 76 (2007) 024315. 28 May 2008 NEMO�3 Neutrino08 13 [3] V.A.Rodin et al., Nucl.Phys. A 793 (2007) 213.

  14. From NEMO�3 to SuperNEMO M × × × ε × ε × ε ε × T obs × × � @ = �;%� � ββ0ν ��?�7��%� × × A N 90 SuperNEMO NEMO�3 82 Se � baseline 100 Mo isotope ( 150 Nd if it can be enriched) isotope mass M 100�200 kg 7 kg efficiency ε ε ε ε 18 % >� 30 % 208 Tl ≤ ≤ 2 ≤ ≤ 2 � 2 2 � Bq/kg � � 208 Tl: < 20 � � � � Bq/kg internal contaminations ��� �� �� : 214 Bi ≤ ≤ ≤ ≤ 10 � � � � Bq/kg 214 Bi: < 300 � � Bq/kg � � 208 Tl and 214 Bi in the ββ ββ ββ foil ββ energy resolution (FWHM) 8% @ 3MeV 4% @ 3 MeV 0νββ ) > 2 x 10 24 y 0νββ ) > 10 26 y T 1/2 ( 0νββ T 1/2 ( 0νββ 0νββ 0νββ 0νββ 0νββ <m ν ν > < 0.3 – 0.9 eV <m ν ν > < 0.04 � 0.11 eV ν ν ν ν See SuperNEMO poster 28 May 2008 NEMO�3 Neutrino08 14

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