1. First results from NEMO 3 Experiment V. Vasiliev (ITEP), H. Ohsumi (Saga) and Ch. Marquet (CENBG) @NDM03, Nara, Japan, June 2003 NEMO collaboration

2. CENBG, IN2P3-CNRS and University of Bordeaux, France CFR, CNRS Gif sur Yvette, France Czech Technical University, Prague, Czech Republic INEEL, Idaho Falls, USA IReS, IN2P3-CNRS and University of Strasbourg, France ITEP, Moscow, Russia JINR, Dubna, Russia Jyvaskyla University, Finland LAL, IN2P3-CNRS and University of Paris-Sud, France LPC, IN2P3-CNRS and University of Caen, France Mount Holyoke College, USA Saga University, Japan University College London, UK NEMO 3 collaboration

3. 1. Introduction (about our final goal) 2. Detector Performances, Present status, Backgrounds 3. An example of background results (Cu foils) 4. Present status of the data analysis 5. Preliminary results of the first stage 6. Conclusions (I) H. Ohsumi (and Ch. Marquet) (II) V. Vassiliev

4. Neutrinoless Double Beta Decays (  Majorana ? ? or new physics ? Measure several isotopes (  100 Mo, 82 Se, 130 Te, 116 Cd, 96 Zr, 48 Ca, 150 Nd Tag and measure all the BG events e -, e +, , , neutron Tracking chamber+Calorimeter+B-field+Shields “zero background” experiment Just to remind you the original idea of NEMO   E(  1 +  2 ) Q  →

5. The NEMO3 detector Fréjus Undergroud Laboratory : 4800 m.w.e. Identification : e -, e +, , n and delayed-    events detection  Measurement of source radiopurity  Background measurement and rejection 3 m 4 m (25 G) B Source :  isotopes (7kg 100 Mo, 1kg 82 Se…..) cylindrical, S = 20 m 2, e = 60  m Tracking detector : He+ alcohol(5%) +Ar(1%) drift wire chamber operating in Geiger mode (6180 cells) Calorimeter : 1940 plastic scintillators coupled to low radioactivity PMs  (E)/E at 3 MeV ~ 3.5% Magnetic field: 25 Gauss Iron shielding: e = 20 cm Neutron shielding: water +wood+parafin 20 sectors

6. 1 sector of NEMO3 Tracking detector (6180 Geiger cells in He+alcohol(5%)+Ar(1%)): Vertex  t = 4 mm,  z = 0.8cm Calorimeter (1940 plastic scintillators – PMTs low radioactivity) FWHM~14% (e  @1 MeV) Iron shield (20cm) + water shield + wood shield + parafin magnetic field B=25 G materials low radioactivity Frejus Underground Laboratory (LSM) 4800m.w.e. NEMO3 : Neutrino Ettore Majorana Observatory

7. October 2001

8. July 2002

9. Sources preparation

10. > 8. 10 24 y < 0,1 – 0,3 eV N Bkg =0,2 evts y -1 kg -1 (90% C.L.) N Bkg =0,02 evts y -1 kg -1 > 1,5 10 24 y < 0,45 – 1,2 eV (90% C.L.)  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 Sensitivity after 5 years :  ) <0,04( 214 Bi) <0,04( 208 Tl)  ),.... Requirements: <0.02mBq/kg( 208 Tl) <0.3mBq/kg( 214 Bi)

11. Component Weight (kg) Petals Iron Wires Copper 40 K 214 Bi 208 Tl 60 Co Not measured <125< 25< 10< 6 <100<0.7<0.3 1.8 .4 <17< 2 2.0 .74.3 .7 <8 10 -3 < 10 -3 <6 10 -4 10 -2 ~20 Shielding Iron 180000 <3000<300 300  100 ~300 60083030018 5000 Total Activities NEMO 3 By ultra low level g-ray spectroscopy with Ge  NEMO (200tons) ~300Bq ( 214 Bi)  Human body (60kg) ~5000Bq ( 40 K)

12.  t ~ 0 ns  t  3 ns  t ~0 ns -- -- e-e- e-e- e + or e -   -- e-e- « Crossing e - » e + e pairs - Double Compton Compton + Möller -- --  t ~0 ns Signal Internal background External background Source contaminations   n source foil How detect signals and tag the background ?  Tracking (Identification e/others) Delayed (<700  s)  track  Calorimeter  (  )~50% (@0.5MeV) Possible for tagging e , e , e , …  Time of flight  t ~300ps(@1MeV) External Background rejection  Magnetic Field (Identification e - /e + ) 3~5% e - /e + confusion @ 1~7MeV  214 Bi Tagged by e(  )  (~164  s) ( 214 Bi-> 214 Po-> 210 Pb)  208 Tl e , e , e , with  (2.6MeV) or Taggd by e(  )  (~300ns) ( 212 Bi-> 212 Po-> 208 Pb)  Neutron Crossing e (4~8MeV) Study of Background Process Identification of e, ,  B=25G  (2 ) decay  (0 ) decay Brief summary of NEMO Performances

13. NEMO-3 STATUS Jan. 2001: first events with 3 first sectors mounted with no magnetic field and no shield Sep. 2001: full detector mounted and assembled Dec. 2001: first events with the full detector with no magnetic field and no shield Feb. 2002: Coil (magnetic field) mounted Mar. 2002: first events with the full detector with magnetic field (no shield) Apr. 2002: Iron shield mounted Jun. 2002  Dec. 2002: Test runs with iron shield + magnetic field ~1500h (1200h) (Period I) Dec. 2002  Feb. 2003: Shutdown for the last tuning (to improve reliability) 14 February 2003 : START TAKING DATA ~2000h (650h) (Period II) (We will mainly report the data of this period) And also: Runs with calibration sources (Sr 90, Bi 207, Co 60 ) for energy and time calibration Runs with neutron source for tracking vertex resolution: for testing neutron shielding (water + wood) Runs for testing iron shield run with and without iron shield Radon studies

14. Z vertex (cm) R  vertex (cm) 1 sector of NEMO3 A vertical flat calibration tube 207 Bi (~220Bq) x 3 x 20 482keV, 976keV (ICE) Run with calibration sources ( 207 Bi example) Distribution of reconstructed vertices Z

15. Geometry of the tracking detector Determination of the vertex 4 rows Tracking curvature 2 rows 3 rows Determination of the impact on the scintillator Resolution on the 2e- channel  R  ) = 0.6 cm  z) = 1.8 cm  ⊥ = 0.4 cm  // = 0.8 cm 8 cathodic wires (0 V) 1 anodic wire (HT  1900 V) vertical drift cells operating on Geiger mode using 2 conversion electrons of 207 Bi

16. Energy Calibration 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 207 Bi 482 keV 976 keV 90 Sr End point 2,28 MeV 207 Bi+ 90 Sr E(keV)=A*ch+B A=3.350±0.034keV/ch B=23.5±9.17 keV

17. Daily survey with a LASER 7 references : 6 PMs coupled to a 207 Bi source + average on all the NEMO3 PMs laser e - 207 Bi 900 PM 5” 1040 PM 3” Photodiode (Intensity Monitor) Optical Filters (known transmissions)  Daily check of E (Gain) and t  PMT E linearity (0 ~ 12MeV)  Determination of t-E relation

18. Gain survey for 3 PMs during 2 months (obtained with the laser system) PM : 2.1.1.4 PM : 18.1.1.0 PM : 19.3.1.0 Typical PM few PMs with pathological behaviour Variation then stabilisation

19. Time Of Flight Rejection External Background (Crossing electron)  events from the foil (  t mes –  t calc ) external hypo. (ns) (  t mes –  t calc ) internal hypo. (ns) An example of 2 track events on 100 Mo Foils Time Alignment (Studied by 60 Co Source)  t ~ 300ps @1MeV

20.  2 event  EVENT OBSERVED BY NEMO-3… 1256 keV 832 keV E 1 +E 2 = 2088 keV (  t)mes –(  t)theo = 0.22 ns (  vertex)  = 2.1 mm (  vertex) // = 5.7 mm

21. 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 

22. 208 Tl Radioimpurity of the 100 Mo (7kg) sources Study of the e -  e -  e -  channels of 208 Tl decay Preliminary, to be improved with more data (NEMO requirement: 20  Bq/kg) Most « dangerous » background for  study Conservative value (90%CL) A( 208 Tl) < 50  Bq/kg 208 Tl channel e  e  e  100 Mo(data) 1 4 0 100 Mo(MC) 1.5 1.7 0.3 (MC calculation for 20  Bq/kg of 208 Tl) (890 hours of data)  e(n  = 5 event

23. 214 Bi effect from Radon 1. Rn level Air in room ~10Bq/m 3 (Normal) Inside of NEMO ~30mBq/m 3 (Very Low) 2. Process (in He+Alcohol gas) where is 214 Bi ? wire ? gas? or foils ? 3. Contributions 2   not dangerous 0   less than 2 events/year ( We are in the border line of our requirement) 4. Radon free air facility This fall  reduce factor 2 Next year  reduce ~50 214 Bi study by NEMO itself Radon monitor for chamber out gas NEMO requirement : to the source 0.3 mBq/kg Electron +  delay track (164  s) 214 Bi  214 Po  210 Pb Sensitivity ~1 mBq/m 3 70 litter 222 Rn 218 Po +(?) 214 Bi + -1500V

24. Comparison neutron simulation with Data from a AmBe source (neutrons:  5MeV +  : E=4,43 MeV) With Iron shield + B=25 G :  4,43 MeV stopped by iron shield  (e  crossing + n  ) DATA Monte Carlo neutrons H Fe+Cu Fe Fast neutrons simulation with 20 cm of iron shield  Expected number of events above 2,75 MeV after 5 years With neutron shield 0 event above 2.75 MeV (After 5 years): with a rejection factor of ~ 70 E>2,75 MeV E  [2,75-3,2] MeV (e - e - )  t=0ns (13,6  4,4) (1,1 +2,2 ) -0,8 Neutron Background n fast e-e- n thermalized Copper frame plastic scintillator AmBe source (out of shield)  Without n shield

25. 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 < 10 -8 n cm -2 s -1 Sensitivity NEMO3 after 1 year 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 < 10 -9 n cm -2 s -1 measured by e - crossing > 4 MeV Sensitivity to 100 kg of isotopes a factor 10 better! a factor 100 better! a factor 10 better! See A. Barabash talk: NEMO extrapolation

26. An Example of Background Results  Cu Foils (0.62kg) （ (I)1200h+(II)650h=1850h  78 days)  Using the same analysis of  decay (Just for an introduction to the next analysis part) 53 events (78days) 0.7 event/day No event above 2.6MeV Cu E 1 +E 2 3MeV

27. Data analisys in NEMO.  2  2 decay analysis. Estimation of background. External  rays. Rn in the tracking chamber Radioactive impurities in source foils Selection of electron-electron (2e) events. Efficiency estimation. Half-life value. Consistence of experimental energy and angular distributions with MC.  2  0 decay analysis. Search for candidate 2  0 events. Estimate efficiency. Estimate background. Conclusion about half-life and neutrino mass.

28. Background, external .  electron+  events Time of flight  incoming  Good agreement

29. Background, Rn in the gas.  electron+  events TOF  decay near the source  electron+ delayed 

30. Background, pollution in source.  single electron events  Ge detector Good agreement keV Single electron energy

31. Selection of electron-electron events. 2 tracks reconstructed + 2 associated PMTs each particle has negative charge electron energy > 200 keV Time of Flight  decay inside the source common vertex vertex in source material nearest to the source geiger layer is hit no delayed geiger hits near the vertex

32. Mo 2  2 preliminary results. 650 hours 13750 events S/B = 40 Background substracted 2  2 Monte Carlo NEMO 3

33. Mo 2  2, angular distribution. Background substracted NEMO 3 2  2 Monte Carlo

34. Mo 2  2, HSD and SSD mechanism. HSD, higher levels contribute to the decay SSD, 1+ level dominates in the decay Abad et al., 1984, Ann. Fis. A 80, 9 Calculations for Mo: F. Simkovic et al., J. Phys. G, 27 (2001) 2233-2240 Effect in one electron spectrum NEMO High 2  2 statistics Measures each electron could see it!

35. Mo 2  2 electrons energy. Background substracted Different predictions for T1/2: NEMO 3

36. Mo 2  0 preliminary result. 2  0 energy region [2.75,3.2] MeV 1 event 2  0 candidate, 650 h. of data analysed, no laser corrections.  = 10 % Conservative limit  2  0 decay energy region [2.6,3.2] MeV 9 candidate event (650 h.), 5 expected.  = 0.7 % Conservative limit  2  0  decay

37. Se 2  2 preliminary result. 1850 hours 400 events S/B = 4 Background substracted Contaminated with  -emitters Cuts: E > 300 keV, Cos (  ) < 0.7 NEMO 3 2  2 Monte Carlo

38. 1850 hours 336 events S/B = 3.4 Background substracted Cd 2  2 preliminary result. 2  2 Monte Carlo NEMO 3

39. 1850 hours 147 events S/B = 3.1 Background substracted Nd 2  2 preliminary result. 2  2 Monte Carlo NEMO 3

40. Conclusion. NEMO 3 is taking data with stable conditions. Tracking chamber and calorimeter pe ｒ forme as expected. First portion of data analysed and preliminary results for 2  2 decay of Mo, Se, Cd and Nd were obtained. Results for 2  2 decay of other isotopes (Ca, Zr, Te) are expected end of the year, and for Mo decay on the excited states will be available soon. Search for neutrinoless and majorana 2  decay is in progress.

41. Summary.