The NEMO3 Double Beta Decay Experiment Ruben Saakyan IoP meeting on Double Beta Decay Manchester 21 November 2007

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester 2 Outline Introduction The detector Results Future

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester 3 A “pragmatic” introduction >.. AA M. t N Bkg.  E ln2. N k C.L. (y) M: masse (g)  : efficiency K C.L. : Confidence level N: Avogadro number t: time (y) N Bckg : Background events (keV -1.g -1.y -1 )  E: energy resolution (keV)   NEMO3 philosophy: - Isotope choice flexibility - Focus on lowering N Bkg - Search for any lepton violating process including with continuum spectrum (e.g. Majoron) Detect  topology!

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester 4 NEMO3 (Neutrino Ettore Majorana Observatory) 50 physicists, 17 institutions

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester 5 3 m 4 m B (25 G) 20 sectors Source : 10 kg of  isotopes cylindrical, S = 20 m 2, e ~ 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 coupled to low radioactivity PMTs Magnetic field: 25 Gauss Gamma shield: Pure Iron (e = 18 cm) Neutron shield: 30 cm water (ext. wall) 40 cm wood (top and bottom) (since march 2004: water  boron) Particle ID: e , e ,  and  The NEMO3 detector Fréjus Underground Laboratory : 4800 m.w.e.

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester 6  isotope foils scintillators PMTs Calibration tube Cathode rings Wire chamber

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester Mo kg Q  = 3034 keV 82 Se kg Q  = 2995 keV 116 Cd 405 g Q  = 2805 keV 96 Zr 9.4 g Q  = 3350 keV 150 Nd 37.0 g Q  = 3367 keV Cu 621 g 48 Ca 7.0 g Q  = 4272 keV nat Te 491 g 130 Te 454 g Q  = 2529 keV  measurement External bkg measurement  search (Enriched isotopes produced by centrifugation in Russia)  decay isotopes in NEMO-3 detector

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester Mo foils Scintillator + PMT Longitudinal view Transverse view Vertex of the e  e  emission  event selection: 2 tracks with Q<0 (right curvature for electrons) 2 PMT hits associated with tracks Common vertex Internal event from the foil (ToF cut) No PMT hits without tracks (  rejection) No delayed short tracks (  rejection from 214 Bi- 214 Po)

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester Tl: Analysis channels: (e -,2  ), (e -,3  ) events coming from foils 214 Bi Analysis channel: (e -, ,  ) events from gas(Radon) or from foil NEMO 3 can measure each component of its background by using different analysis channels Internal background

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester 10 Crossing electron > 4 MeV e.g neutron capture in Cu Electron – positron pair. Rejection with magnetic field External background Control and reject backgrounds Unprecedented understanding of backgrounds

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester 11 1 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 Phase I : February 2003 – September 2004 (radon background in data) ~ 1 0 -like event/y/kg with 2.8 < E 1 +E 2 < 3.2 MeV Radon trapping facility Inside the NEMO 3 tent: factor of 100 – 300 Inside NEMO 3: almost factor of 10 A( 222 Rn)  3 mBq/m 3 Phase II : since October 2004 (radon level reduced by a factor of 10)

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester 12 NEMO3 Results

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester 13 Cos(  ) Angular distribution events 6914 g 389 days S/B = 40 NEMO Mo E 1 + E 2 (MeV) Sum energy spectrum events 6914 g 389 days S/B = 40 NEMO Mo Background subtracted Data 2  2 Monte Carlo Data 2  2 Monte Carlo Background subtracted «  factory» → tool for precision test T 1/2 (  ) = 7.11  0.02 (stat)  0.54 (syst)  years Number of events Number of events/0.05 MeV 100 Mo  2 results Phys. Rev. Lett (2005) Phase 1: Feb – Dec “High Radon”

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester g 389 days 2750 events S/B = 4 48 Ca 82 Se Preliminary results for ~360 d Phase I data. Additional statistics are being analysed and to be published soon. 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 Background subtracted  2 results with other nuclei  is important: 1) Experimental input to NME calculation (see next slide) 2) Ultimate background for  2) Ultimate background for 

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester 15 g pp fixed from experimentally measured M 2 Error bars are from experimental errors on T 1/2 2 V.A. Rodin et al., Nucl. Phys. A 766, 107 (2006) - Erratum 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 11 HSD  2 /ndf = 254 / 42 SSD  2 /ndf = 42,3 / 42 SSD mechanism established from 100 Mo single e- spectra Ru

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester 16 New results: 130 Te  S + B = 607 events 109 events 454 g 534 days S/B = 0.25 Preliminary result: 130 Te:T 1/2 = [ 7.6 ± 1.5 (stat) ± 0.8 (syst) ]  y Previous indication on effect from a direct experiment (6.1 ± 1.4 (syst) ± ) x years (Arnaboldi 2003)

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester 17 How constant are coupling constants?  is sensitive to G f variations (~G f 4 )  decay was first detected in geochemical experiments ( 130 Te  130 Xe) Daughter isotope ( 130 Xe) extracted from an old mineral and number of atoms counted old minerals (~10 6 – 10 9 yr) extractor and mass-spectrometer 130 Te geochemical measurements: (25 ± 2) x yrs (Kirsten 83) (27 ± 2) x yrs (Bernatowicz 93) (8 ± 1) x yrs (Manuel 91, Takaoka 96) “old” samples (~10 9 yrs) “new” samples (few x 10 6 yrs) NEMO3 result (“present”  rate): (7.6 ± 1.7) x yrs Difference between  rates in past and present due to time dependence of Fermi constant??? Suggestion: Carry out geochemical isotope analyses with 100 Mo  100 Ru, 96 Zr  96 Mo (daughter not gas) etc and compare with direct measurements (precise NEMO3 results available).

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester 18 Event 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  decay to excited states Decay to the excited 0 + state (1130keV) of 100 Ru T 1/2 = (stat)  0.8 (syst)  y Nuclear Physics A781 (2006) Important for NME calculations!

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester 19  of 100 Mo and 82 Se 693 days of data Phase I + Phase II 693 days of data Phase I + Phase II 100 Mo 82 Se T 1/2 > 5.8 × % C.L.  m  < (0.8 – 1.3) eV [1-3] T 1/2 > 5.8 × % C.L.  m  < (0.8 – 1.3) eV [1-3] T 1/2 > 2.1 × % C.L.  m  < (1.4 – 2.2) eV [1-3] T 1/2 > 2.1 × % C.L.  m  < (1.4 – 2.2) eV [1-3] Both simple counting and likelihood methods are consistent [1] M.Kortelainen and J.Suhonen, Phys.Rev. C 75 (2007) (R). [2] M.Kortelainen and J.Suhonen, Phys.Rev. C 76 (2007) [3] V.A.Rodin et al., Nucl.Phys. A 793 (2007) 213. [5] M.Aunola et al., Nucl.Phys. A 463 (1998) 207. NME: Data until spring 2006

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester 20  Search. Future. Collaboration decided to perform blind analysis. Plan to open the box and update the results ~ in April 2008 (in time for Neutrino’08) and once again at the end of the experiment ~ early expected sensitivities in 2010: 100 Mo T 1/2 (0  ) > 2 × y (90 % CL)  m  < (0.4 – 0.7) eV 82 Se T 1/2 (0  ) > 8 × y (90 % CL)  m  < (0.7 – 1.1) eV see previous slide for NME used

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester 21 V+A *n=1 **n=2 **n=3 **n=7 ** Mo >3.2∙10 23 <1.8∙10 -6 >2.7∙10 22 g ee <( )∙10 -4 >1.7∙10 22 >1.0∙10 22 >7∙10 19 Se >1.2∙10 23  2.8∙10 -6 >1.5∙10 22 g ee <( )∙10 -4 >6.0∙10 21 >3.1∙10 21 >5.0∙ * PI+PII data ** PI data, R.Arnold et al. Nucl. Phys. A765 (2006) 483 World’s best limits n: spectral index, limits on half-life in years Other  mechanisms Majoron emission

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester 22 Summary NEMO3 – unique approach combining tracking and calorimetry Unprecedented understanding of backgrounds  factory: precise high statistic measurement of 7 isotopes (out of 9 main candidates!). 5 publications in preparation – Experimental input for NME calculations – Understanding  as background

21/11/2007 R. Saakyan: NEMO3, IoP DBD meeting, Manchester 23 Summary(2) < eV so far. Blind analysis underway. Worlds best limits on other  modes (V+A, Majoron) Data taking until end < eV. Partly cover Klapdor’s claim, discovery possible! Ideal test bench for future generation  experiments. Exciting times. Watch this space!