 NEMO-3 Detector  Preliminary results Performance of the detector  analysis for 100 Mo, 82 Se and 150 Nd  Background study for  research ( 208 Tl and Radon)  Future of NEMO NEMO Experiment Neutrino Ettore Majorana Observatory Journées Neutrinos novembre 2003 LPNHE-Paris Xavier Sarazin for NEMO Collaboration

NEMO Experiment Neutrino Ettore Majorana Observatory  Search for neutrinoless double beta decay  Study several isotopes Mo 100, Se 82, Te 130, Cd 116, Zr 96, Ca 48, Nd 150  Tag and measure all the components of background e -, e +, , , neutrons “zero background” experiment

Double beta  (0 ) decay : Physics beyond the standard model  (0 ) : 2n  2p+2e -  L = 2 Process  Majorana Neutrino  and effective mass  Right-handed current in weak interaction  Majoron emission  SUSY particle exchange WW WW n n p p ee ee M eR eL (Q  ~ MeV) ( ) h h

1 sector of NEMO3  Sources: 20 m 2, total mass ~ 10 kg, thickness ~ 60 mm  Tracking detector (6180 Geiger cells in He+alcohol): Vertex  t = 5 mm,  z = 1 cm  Calorimeter (1940 plastic scintillators + PMTs low radioactivity)  E /E = 3% at 3 MeV   and neutron shield: Iron shield (18 cm) + water shield + wood shield + parafin  magnetic field B=25 G  all materials low radioactivity (total activity in 208 Tl and 214 Bi  300 Bq) Located in Modane Underground Laboratory NEMO-3 Detector

 isotope foils scintillators PMTs Calibration tube Cathodic rings Wire chamber

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

coil Iron shield Water tank wood

Sources preparation

 Bkg Sources   thickness  mg/cm 2 ) Q  = 3034 keV Q  = 2995 keV 82 Se (0.93 kg) 100 Mo (6.9 kg) Sources in NEMO-3 detector

Expected background and sensitivity External and neutron background negligeable 7 kg of 100 Mo Source contamination : A ( 214 Bi) < 0.3 mBq/kg A ( 208 Tl) < 0.02 mBq/kg Internal background : 214 Bi < 0.04 evts/y/kg 208 Tl < 0.04 evts/y/kg  0.11 evts/y/kg Total Bkg < 1.4 event/year T 1/2 (0 ) > y  m  < 0.1 – 0.3 eV 5 years of data Energy window: [ ] MeV Efficiciency  = 14% 1 kg of 82 Se Source contamination : A ( 214 Bi) = 1.2  0.5 mBq/kg (measured) A ( 208 Tl) = 0.4  0.1 mBq/kg Internal background :  0.01 evts/y/kg Hot spots: Pollution rejected Bkg ~ 0 event/year T 1/2 (0 ) > y  m  < 0.6 – 1.2 eV

NEMO-3 Preliminary Results Performance of the detector  analysis for 100 Mo, 82 Se, 150 Nd Background analysis for  search

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: Type of eventRate (mHz) 1 e , 0  e , N  150 e  e  pairs110 Crossing e  80  event 5.4 mHz Data Tacking October 1 st days of data tacking ~ 75 % efficiency Days of data collecting / month Efficiency of data collecting / month

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

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

Performances of the calorimeter Tube in each sector where calibration sources are introduced (3 positions) 3 electron energies : 486 keV and 976 keV with 207 Bi, and 2.28 MeV with 90 Sr 90 Sr End point 2,28 MeV At 1 MeV (Q   3 MeV for 100 Mo and 82 Se): 207 Bi 482 keV 976 keV FWHM = 135 keV FWHM  E /E Ext. Wall (PMTs 5") 14 % 5.8 % /  E( MeV ) Int. Wall (PMTs 3") 17 % 7.1 % /  E( MeV )

 2 event  EVENT OBSERVED BY NEMO-3… E 1 +E 2 = 2088 keV (  t)mes –(  t)theo = 0.22 ns (  vertex)  = 2.1 mm (  vertex) // = 5.7 mm

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

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

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

82 Se 2  2 preliminary results (14 Feb – 30 Sep. 2003) Contaminated with low energy  -emitters Cuts: E > 300 keV Cos (  ) < hours 1100 events S/B = 4.2 Background substracted 2  2 Monte Carlo T 1/2 = 9.52  0.25 (stat)  0.9 (syst)  y

150 Nd 2  2 preliminary results (June 2002 – 30 Sep. 2003) 3834 hours 400 events S/B = 4.2 Background substracted 2  2 Monte Carlo T 1/2 = 7.5  0.3 (stat)  0.7 (syst)  y

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

 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  s) to tag delayed  from Bi Bi  214 Po (164  s)  210 Pb How NEMO-3 tags the background

Measurement of the sources of background 214 Bi channel e  (  with T 1/2 (  )  164  s ( 214 Bi -  214 Po -  210 Pb  ) 208 Tl channels e   ’s with E  = 2.6 MeV 212 Bi  212 Po e  (  )  T 1/2 (  )  300 ns neutrons, external gammas e  crossing, e  e , e  e  > 4 MeV

Electron + N  ’s 208 Tl (E  = 2.6 MeV) Electron crossing > 4 MeV Neutron capture BACKGROUND EVENTS OBSERVED BY NEMO-3… Electron +  delay track (164  s) 214 Bi  214 Po  210 Pb Electron – positron pair B rejection 

Search for 208 Tl background in the foils 3800 h of data analysed 14 Feb – 30 Sep 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 look for e , e2 , e3  events coming from the foil sourcesN eventsA (  Bq/kg) HPGe measure 100 Mo  Mo metal  40 < Mo comp.350< 110 Cu0 82 Se   Nd   2000 nat Te5~250< 90 VERY PRELIMINARY Good agreement with the HPGe measurements

Neutron and High-Energy gamma Background Only 1  -like event > 4 MeV detected after 160 days of data tacking ! (14 Feb – 30 Sep. 2003) Run 2058 event March Te source (sector 19) E 1 +E 2 = 4448 keV look for e  e  events > 4 MeV coming from the foil

Two different measurements of radon in the NEMO-3 gas: Radon detector: sensitivity: 1 count/day for 1 mBq/m 3 Radon measurement  20 mBq/m 3 (1e  + 1  ) channel in the NEMO-3 data: Able to measure Radon every half day Radon measurement  30 mBq/m 3 ~ a few  0 -like  events 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 ~ Rn 218 Po 214 Pb 214 Bi 214 Po 210 Pb Radon in NEMO-3    s

E1+E2= 2880 keV Run 2220, event , May 11th 2003 a  -like event due to Radon from the gas  track (delay = 70  s) 214 Po  210 Pb 214 Bi  214 Po  decay IN THE GAS

Fall 2003 : Tent surrounding the detector A( 222 Rn) ~ Bq/m 3 Today : A( 222 Rn) in the LSM ~10 Bq/m 3 Spring 2004 : Radon-free Gas Facory A( 222 Rn) ~ 0.2 Bq/m m 3 /h Free-Radon Purification System

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 < n cm -2 s -1 Sensitivity NEMO3 after 2 years of data :  208 Tl in source foils < 2  Bq/kg channel e  ’s (E  = 2.6 MeV) 212 Bi  212 Po e  (300 ns)  214 Bi in source foils < 2  Bq/kg measured by channel e (   ( 214 Bi  214 Po  210 Pb; T 1/2 = 164  s )  neutrons < n cm -2 s -1 measured by e - crossing > 4 MeV Sensitivity to 100 kg of isotopes

Future for a NEMO Detector Tracking-Calorimeter Technique

NEMO-3 QD IH QD IH Expected values of  m  from neutrinos oscillations parameters Pascoli and Petcov, hep-ph/ (best fit atm + sol ) Quasi-Degenerate (QD):  m  > 0.6 eV Inverted Hierarchie (IH): eV <  m  < 0.6 eV Normal Hierarchie (NH):  m  < eV ~ ~ ~ ~ Next Generation of NEMO detector « detect » 1 gold event/year with  m  ~ 20 meV

Number of  event detected / year: ln2. N. . M A. T 1/2 (y) 0 N  / year  N : Avogadro A : atomic mass M : mass (g) of  enrich. Isotope  : detection efficiency Future of NEMO Real measurement with 1 GOLD EVENT / YEAR M = k  100 kg of 100 Mo or 82 Se  = 0.5 Background = 0.1 event / year 1  Gold event detected / year 0 T 1/2  2  k years  m  = 20 – 60 meV Goal of a next NEMO detector:

3-4-5 December 2003: 1 st 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 ( 100 Mo, 82 Se, 150 Nd…) Purification sources Simulation Main challenges: Energy resolution Efficiency Sources (enrichment, purification) Future of NEMO

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

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

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

CONCLUSIONS  NEMO-3 Detector running since 14 Feb Data tacking efficiency ~75%  Performance of the detector has been reached !   preliminary results for 100 Mo, 82 Se and 150 Nd already more than  events collected  Background study for  search: 208 Tl (e  N  channel) : good agreement with HPGe measurements Neutrons and High-energy  : only 1  -like event > 4 MeV ! Radon: mBq/m3 inside the detector a few  -like events/year expected Too high !  Free radon purification system under construction Radon/8 in Feb 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  m  ~ 20 meV