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  & 0  & 0  ) Conclusion

Introduction

Double beta decay Two-neutrino  decay (2  ):(A,Z)  →  (A,Z+2) + 2 e  + 2 e 0  & 0  :  L = 2 process Majorana neutrino ≡ and effective mass  m  Light neutrino exchange →  m  Right-handed (V+A) current in weak interaction →  m ,  Majoron emission →  g M  SUSY particle exchange →        with Majoron emission (0  ):(A,Z)  →  (A,Z+2) + 2 e  +  Neutrinoless  decay (0  ):(A,Z)  →  (A,Z+2) + 2 e  WW n n p p ee ee M WW eR eL h h 0 

Neutrinoless Double Beta Decay arbitrary units (Q  ~ MeV) Two electron energy spectrum Experimental signature: 2 electrons E 1 +E 2 = Q   0 = (T 1/2 ) -1 = G 0 (Q  5,Z) |M 0 | 2  m  2 G 0 – phase space factor M – nuclear matrix element  m  – effective neutrino mass  m  = |  j |U e j | 2 e i  j m j |

NEMO 3 description

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

B (25 G) 4 m 20 sectors 3 m 6 m Detector located in the Fréjus Underground Laboratory, France (4800 m.w.e.) Source: 10 kg of  isotopes, cylindrical, S = 20 m 2, foils ~ 60mg/cm 2 Tracking detector: drift wire chamber operating in Geiger mode (6180 cells) gas = 94% 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 (18 cm layer) Neutron shield: borated water (ext. wall, 30 cm layer) & wood (top and bottom, 40 cm layer) NEMO 3 detector identification of e –, e +,  and  -particles

116 Cd 405 g Q  = 2805 keV 96 Zr 9.4 g Q  = 3350 keV 150 Nd 37.0 g Q  = 3367 keV 48 Ca 7.0 g Q  = 4272 keV 130 Te 454 g Q  = 2529 keV nat Te 491 g Cu 621 g 2  decay measurement External background measurement 100 Mo kg Q  = 3034 keV 0  decay search 82 Se kg Q  = 2995 keV & NEMO 3 sources

 event from data Deposited energy: E 1 + E 2 = 2088 keV Internal hypothesis: (  t) mes – (  t) theo = 0.22 ns Common vertex: (  vertex)  = 2.1 mm (  vertex) // = 5.7 mm Run Number: 2040 Event Number: 9732 Date: Mo foils Scintillator + PMT Longitudinal view Transverse view Vertex of the e  e  emission

External background 208 Tl (PMTs) Measured with (e   ) external events ~  -like events y -1 ·kg -1 with 2.8<E 1 + E 2 <3.2 MeV ~  -like events y -1 ·kg -1 with 2.8<E 1 + E 2 <3.2 MeV 208 Tl impurities inside the foils Measured with (e  2  ), (e  3  ) events coming from the foil External neutrons and high energy  ’s Measured with (e  e  ) int events with E 1 +E 2 > 4 MeV   -like events y -1 ·kg -1 with 2.8<E 1 + E 2 <3.2 MeV NEMO 3 can measure each component of its background! 100 Mo 2  decay T 1/2 = 7.1 × y ~  -like events y -1 ·kg -1 with 2.8<E 1 + E 2 <3.2 MeV Background measurement

Radon background ~ 1 0 -like event/y/kg with 2.8 < E 1 +E 2 < 3.2 MeV Radon was the dominant background for the 0  search in the NEMO 3 Phase I data !!! Radon was the dominant background for the 0  search in the NEMO 3 Phase I data !!! 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(Rn) in the lab ~15 Bq/m 3 Two independent measurements of radon in the NEMO 3 gas Good agreement between the two measurements 1.Radon detector at the input/output of the NEMO 3 gas 2.(1e  + 1  ) channel in the NEMO 3 data A(Rn) inside NEMO 3  mBq/m 3 (Phase I) 222 Rn (3.8 days) 218 Po 214 Pb 214 Bi 214 Po 210 Pb    s Decay in the gas  delayed  214 Bi → 214 Po (164  s) → 210 Pb  

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

Radon trapping facility chilling unit charcoal columns compressor buffer dryer

NEMO 3 results

100 Mo: 2  decay T 1/2 = [ 7.11 ± 0.02 (stat) ± 0.54 (syst) ]  y Phys. Rev. Lett. 95 (2005) T 1/2 = [ 7.11 ± 0.02 (stat) ± 0.54 (syst) ]  y Phys. Rev. Lett. 95 (2005) events 6914 g 389 days S/B = 40 cos(  ee ) Data 2 MC simulation Background subtracted Sum Energy SpectrumAngular Distribution Data 2 MC simulation Background subtracted events 6914 g 389 days S/B = 40 E 1 + E 2 (MeV)

2 HSD MC simul. Background subtracted Data E single (keV) HSD  2 /ndf = 139./36 E single (keV) 2 HSD MC simul. Background subtracted Data SSD  2 /ndf = 40.7/36 Single electron energy distribution of the 2  decay of 100 Mo in favor of Single State Dominance (SSD) model Single electron energy distribution of the 2  decay of 100 Mo in favor of Single State Dominance (SSD) model Single electron spectrum different between SSD and HSD Šimkovic et al., J. Phys. G 27 (2001) E single (keV) HSD, higher levels contribute to the decay SSD, 1 + level dominates in the decay Abad et al., Ann. Fis. A 80 (1984) Mo Tc 1+1+

100 Mo:  decay to exc. states 2  decay to the state: S/B = 3.0 T 1/2 =[ (stat) ± 0.8(syst)]  y 0  decay to the state: T 1/2 > 8.9  % C.L. 2  decay to the state: T 1/2 > 1.1  % C.L. 0  decay to the state: T 1/2 > 1.6  % C.L. To be published soon, submitted to Nucl. Phys. A 2  decay to the state: S/B = 3.0 T 1/2 =[ (stat) ± 0.8(syst)]  y 0  decay to the state: T 1/2 > 8.9  % C.L. 2  decay to the state: T 1/2 > 1.1  % C.L. 0  decay to the state: T 1/2 > 1.6  % C.L. To be published soon, submitted to Nucl. Phys. A Clear topology: : 2e  in time & energy and TOF cuts : 2e  in time & energy and TOF cuts 100 Mo (540 keV) (1130 keV) (1227 keV) 0 + (g.s.) 100 Ru (1362 keV) 3034 keV 11 2 days of data (Phase I)

100 Mo: 0  decay Energy window: 2.78 MeV < E ee < 3.20 MeV 14 events observed, 13.4 events expected 7.9 events excluded at 90% C.L. V-A: T 1/2 > 5.8 × % C.L.  m  < (0.6 – 0.9) eV [1-3], < (2.1 – 2.7) eV [4] V+A: T 1/2 > 3.2 × % C.L.  < 1.6 × [5] Energy window: 2.78 MeV < E ee < 3.20 MeV 14 events observed, 13.4 events expected 7.9 events excluded at 90% C.L. V-A: T 1/2 > 5.8 × % C.L.  m  < (0.6 – 0.9) eV [1-3], < (2.1 – 2.7) eV [4] V+A: T 1/2 > 3.2 × % C.L.  < 1.6 × [5] 693 days of data Phase I + Phase II [1] F.Šimkovic et al.,Phys.Rev. C 60 (1999) [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:

T 1/2 = [ 9.6 ± 0.3 (stat) ± 1.0 (syst) ]  y Phys. Rev. Lett. 95 (2005) T 1/2 = [ 9.6 ± 0.3 (stat) ± 1.0 (syst) ]  y Phys. Rev. Lett. 95 (2005) events 932 g 389 days S/B = 4 Sum Energy Spectrum Data 2 MC simulation Background subtracted E 1 + E 2 (MeV) 82 Se: 2  decay

82 Se: 0  decay Energy window: 2.62 MeV < E ee < 3.20 MeV 7 events observed, 6.4 events expected 6.2 events excluded at 90% C.L. V-A: T 1/2 > 2.1 × % C.L.  m  < (1.2 – 2.5) eV [1-3], < (2.6 – 3.2) eV [4] V+A: T 1/2 > 1.2 × % C.L.  < (2.8 – 3.0) × [6] Energy window: 2.62 MeV < E ee < 3.20 MeV 7 events observed, 6.4 events expected 6.2 events excluded at 90% C.L. V-A: T 1/2 > 2.1 × % C.L.  m  < (1.2 – 2.5) eV [1-3], < (2.6 – 3.2) eV [4] V+A: T 1/2 > 1.2 × % C.L.  < (2.8 – 3.0) × [6] 693 days of data Phase I + Phase II [1] F.Šimkovic et al.,Phys.Rev. C 60 (1999) [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:

Preliminary results: 116 Cd:T 1/2 = [ 2.8 ± 0.1 (stat) ± 0.3 (syst) ]  y (SSD) 150 Nd:T 1/2 = [ 9.7 ± 0.7 (stat) ± 1.0 (syst) ]  y 96 Zr:T 1/2 = [ 2.0 ± 0.3 (stat) ± 0.2 (syst) ]  y Preliminary results: 116 Cd:T 1/2 = [ 2.8 ± 0.1 (stat) ± 0.3 (syst) ]  y (SSD) 150 Nd:T 1/2 = [ 9.7 ± 0.7 (stat) ± 1.0 (syst) ]  y 96 Zr:T 1/2 = [ 2.0 ± 0.3 (stat) ± 0.2 (syst) ]  y 116 Cd, 150 Nd, 96 Zr: 2  decay E 1 +E 2 (MeV) 116 Cd 150 Nd 96 Zr 2  simul. Data 2  simul. Data 2  simul. Data 818 events 37 g days S/B = evts 405 g days S/B = events 5.3 g days S/B = 0.9 Background subtracted

48 Ca: 2  decay Preliminary result: 48 Ca:T 1/2 = [ 3.9 ± 0.7 (stat) ± 0.6 (syst) ]  y Preliminary result: 48 Ca:T 1/2 = [ 3.9 ± 0.7 (stat) ± 0.6 (syst) ]  y 40 events 7.0 g days S/B = 15.7 Very small background! Phase I + Phase II data E e > 0.7 MeV & cos(  ee ) < 0 E 1 +E 2 (MeV) 48 Ca

0 decay Netrinoless  decay with Majoron emission (A,Z) → (A,Z+2) + 2e  +  0 [1] F.Šimkovic et al.,Phys.Rev. C 60 (1999) [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: 100 Mo: T 1/2 > 2.7 × % C.L.  g ee  < (0.5 – 1.9) × Mo: T 1/2 > 2.7 × % C.L.  g ee  < (0.5 – 1.9) × Se: T 1/2 > 1.5 × % C.L.  g ee  < (0.7 – 1.7) × Se: T 1/2 > 1.5 × % C.L.  g ee  < (0.7 – 1.7) × Nucl. Phys. A 765 (2006) days of data (Phase I)

Conclusion

New measurement and T 1/2 limits for  decay of 100 Mo to excited states Conclusion No signal seen for 0  decay Improved limits: 100 Mo:T 1/2 > 5.8 × y,  m  < (0.6 – 2.7) eV 82 Se:T 1/2 > 2.1 × y,  m  < (1.2 – 3.2) eV Improved limits for 0  decay of 100 Mo and 82 Se 2  decay of 100 Mo and 82 Se measured with high statistics Preliminary results for other isotopes Analysis of Phase II data in progress

Spare Slides About SuperNEMO

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

extension of the NEMO 3 technique 100–200 kg of isotopes, thin source between tracking volumes, surrounded by calorimeter. sensitivity T 1/2 (0  ) > y,  m  < 50 meV main improvements needed:  energy resolution 3 MeV = 4%)  detection efficiency (factor of 2)  source radio purity (factor of 10)  background rejection methods SuperNEMO Project

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

14 m 3 m 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 Water shield: 2kT of water for 20 modules Source foil: 5 kg of enriched 150 Nd or 82 Se Number of modules = 20  (0  ) ~ 30 % Possible Design

Goal : T 1/2  y  m   50 meV The best choice for phase space and background Q   = MeV 150 Nd Radiopurity requirements for the  source 208 Tl < 2  Bq/kg T 2 = 9 x10 18 y  Expected background from 2  = 2.2 evt/500kg.y in 200 keV Enrichment by laser (200 keV energy window at Q  ) Phase space factor G 0 = 8.00 x y -1 eV -2  Sources = G  M   m  2  T 1 2 Q  = MeV Phase space factor G 0 = 1.08 x y -1 eV Se T 2 = 9 x y  Expected background from 2  = 1.4 evt/500kg.y in 200 keV Enrichment by ultracentrifugation 214 Bi < 10  Bq/kg 208 Tl < 2  Bq/kg Rn < 2  Bq/m 3 Radiopurity requirements for the  source (200 keV energy window at Q  )