M. Dracos, CEA, 10/04/ Double Beta experiment with emulsions?

M. Dracos, CEA, 10/04/ Double Beta Decay ? T 1/2 ~ years ! Observed for: Mo 100, Ge 76, Se 82, Cd 116, Te 130, Zr 96, Ca 48, Nd 150 allowed double beta double beta without neutrino Isotope Q   (keV) 116 Cd  116 Sn  Se  82 Kr  Mo  100 Ru  Zr  96 Mo  Nd  150 Sm  Ca  48 Ti  4.1 The NEMO3 experiment

M. Dracos, CEA, 10/04/ The NEMO3 detector Sources : 10 kg, 20 m 2 wire chamber (Geiger) 3m energy and time of flight measurements plastic scintillator blocks 2 electron tracks + photomultipliers (Hamamatsu 3", 5") expected sensitivity up to m ~0.3 eV

M. Dracos, CEA, 10/04/ Event Examples

M. Dracos, CEA, 10/04/2008 5Results 932 g 389 days 2750 even. S/B = 4 82 Se 82 Se T 1/2 = 9.6  0.3 (stat)  1.0 (syst)  y 116 Cd T 1/2 = 2.8  0.1 (stat)  0.3 (syst)  y 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 48 Ca T 1/2 = 3.9  0.7 (stat)  0.6 (syst)  y 48 Ca background subtracted Phase I + II 693 days T 1/2 (  ) > (90 % C.L.)  < eV Expected in 2009 T 1/2 (  ) > (90 % C.L.)  < eV 100 Mo ( 7 kg )

M. Dracos, CEA, 10/04/ Super NEMO Improvements: –Energy resolution 15%   E/E = 3 MeV –Efficiency 15%  MeV –Source x10 larger 7kg  kg Most promising isotopes – 82 Se (baseline) or perhaps – 150 Nd Aim: T 1/2 > 2 x y   M   < meV R&D up to 2009, construction between 2010 and 2013 source sheet

M. Dracos, CEA, 10/04/ e e 2  with emulsions "veto" emulsion, if needed (~50  m like in OPERA?) plastic base "2  " emulsion thick enough to detect up to 4 MeV electrons (density?) beta source (~50  m inNEMO could be less for emulsions)

M. Dracos, CEA, 10/04/ Tests in Nagoya using OPERA emulsions A. Ariga, diploma thesis 50  m

M. Dracos, CEA, 10/04/  with emulsions 1 MeV e- 2 MeV e- (Akitaka Ariga) simulation

M. Dracos, CEA, 10/04/  with emulsions NEMO3 surface: 20 m 2 Super-NEMO surface: 10x20 m 2 To cover the same isotope source surface with emulsions (both sides to detect the 2 electrons) we need an emulsion surface: 2x200=400 m 2. Just for comparison, one OPERA emulsion has about m 2 and one brick m 2. So 400 m 2 is about the equivalent of 600 OPERA bricks over (but not with the same thickness of course…). Use the same envelops like the OPERA changeable sheets by introducing at the middle of the two emulsions a double beta source sheet, or use longer emulsion sheets easier to handle by microscopes. Keep all these envelops for some time (e.g months depending on fading) in the experiment and after this period start scanning them one after the other. They could be replaced by new envelops during 5 years in order to accumulate something equivalent to what Super-NEMO could do:  400*5 year*m 2

M. Dracos, CEA, 10/04/ cm 2 / h TS(1994)NTS(1996)UTS(1998)SUTS(2006)SUTS(2007-) Scanning Power Roadmap 1stage facility CHORUSDONUTOPERA 2  with emulsions How much time is needed to make a full scan of 2000 m 2 (is a full scan in all volume really needed?)? If the Japanese S-UTS scanning system is used with a speed of 50 cm 2 /hour (be careful with thickness…), for one scanning table: 25 m 2 /year (200 working days/year). By using 16 tables and extracting 100 m 2 /3 months (1 year exposure at the beginning and putting back new emulsions with the same isotopes), this finally will take less than 5 years (as Super-NEMO). Probably the emulsion thickness needed to detect these electrons will need more scanning time and the speed would be significantly less than 50 cm 2 /h. On the other hand, scanning speed increases with time… Nakamura san Nufact07

M. Dracos, CEA, 10/04/ Pending questions Energy resolution for NEMO: 15% for 3 MeV electrons Required for Super-NEMO: lower than 7% (goal 4%) Emulsion experiment energy resolution: ??? (monoenergetic 1 MeV 207 Bi electrons could be used to have a good estimate of this resolution) Reconstruction efficiency for NEMO: 15% Required for Super-NEMO: 40% Emulsion experiment reconstruction efficiency: ?? (here also a well calibrated 207 Bi source or other sources could be used) Minimum electron energy (~1 MeV, 0.5 MeV for NEMO3?) Afforded background? Could magnetic field help (better momentum resolution or  rejection)? Possibility to take thinner isotope sheets (60  m for NEMO3) and have better energy resolution (but also more scanning for the same isotope mass).

M. Dracos, CEA, 10/04/ Extra Ideas e e decreasing density (25 mm layers) to minimize the emulsion thickness and better energy resolution at the end of the track e e emitter in powder (diluted in an emulsion layer) better vertex and energy reconstruction ? after discussion with Fuji engineers, all these ideas are possible!

M. Dracos, CEA, 10/04/ END

M. Dracos, CEA, 10/04/  with emulsions for 400 m 2 /year and 400 m 2 isotopes available isotope block number time (years)surface (m 2 )exposure time (years) surface*time (m 2 *years) total

M. Dracos, CEA, 10/04/ Electron + N  ’s 208 Tl (E  = 2.6 MeV) Electron crossing > 4 MeV Neutron capture Electron +  delay track (164  s) 214 Bi  214 Po  210 Pb Electron – positron pair B rejection  BACKGROUND EVENTS OBSERVED BY NEMO-3

M. Dracos, CEA, 10/04/ E1+E2= 2880 keV Run 2220, event , May 11th 2003  track (delay = 70  s) 214 Po  210 Pb 214 Bi  214 Po  decay IN THE GAS  -like event due to Radon from the gas (NEMO3)

M. Dracos, CEA, 10/04/ NEMO3 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