Shiva King, UCL Dubna December 2007 2nbb Decay of 48Ca Shiva King, UCL Dubna December 2007 18-Sep-18 Shiva King, UCL

Introduction 90Y activity measurement (P1 and P2) 1e1 channel 90Sr Calibration runs Energy cut justification Cos cut Discussion Data period Phase 1 Total run time = 9670 h; 1.10 y Run List as suggested by analysis team Data period Phase 2 Total run time = 12967 h; 1.48 y Run List as suggested by analysis team 18-Sep-18 Shiva King, UCL

Y90 Activity Measurement Single electron events in the Ca48 foil: One track with –ve charge associated with an isolated scintillator hit Energy deposit in scintillator E > 100 keV Track has vertex in the source foil There must be at least 1 hit in layer 0 or 1 Track length > 30cm Not more than 2 unused fast geiger hits <15cm from vertex Alphas: Refiring time > 70ms Single and group delayed hits 18-Sep-18 Shiva King, UCL

Y90 Activity Measurement: Phase 1 (Paris 2007) Y90 activity: 0.031 +- 7.90x10-5(stat) Bq; 1763.88 +- 4.52 (stat) mBq/Kg 18-Sep-18 Shiva King, UCL

Y90 Activity Measurement: Phase 1 90Y activity: 0.03064 +- 0.00444(stat) Bq; 1750.25 +- 1.7 (stat) mBq/Kg 210Bi activity: 4.44842 Bq 3 fixed activities (48Ca gs, 214Bi sfoil/wire) 4 floating activities (90Y, 210Bifoil, 40K, 234Pa) I used the TFractionFitter() function in ROOT No activities found for 40K and 234Pa, I can use the errors from the measurements as a systematic error on these backgrounds Note that my plots start at 0.5 MeV not 0.2 MeV as in Victor’s case 18-Sep-18 Shiva King, UCL

Y90 Activity Measurement: Phase 2 90Y activity: 0.0288 +- 4.419e-5(stat) Bq; 1649.34 +- 1.41 (stat) mBq/Kg 210Bi activity: 3.8763 Bq 18-Sep-18 Shiva King, UCL

2 Spectrum Background (re-cap) There is a historical problem with the 2 spectrum at low energies Cos To tackle this problem, three different analyses have been studied: 1e channel 1e1 channel 90Sr calibration runs 18-Sep-18 Shiva King, UCL

1e1 channel: Phase 1 For the electrons I used the same cuts for the 1e analysis For gammas: Internal probabillity > 4% External probability < 1% 18-Sep-18 Shiva King, UCL

1e1 channel: Phase 1 There is an obvious discrepancy between the data and the background. There are more external background events than internal - this may be due to the fact that not all the internal activities are known (234Pa, 40K…) 18-Sep-18 Shiva King, UCL

90Sr Calibration Runs Ref: V. I Tretyak, Aussois, December 05 The data with two 90Sr sources deposited on the natural molybdenum foils placed in the calibration tubes of the sectors 6 and 16 has been taken the 1st and 2nd July 2004. The source activities have been measured at IReS the 16 of May 2003. No source 11 206 out 16 center 31 +/- 4 199 6 center 40 +/- 5 198 Source orientation Position, sector Activity, Bq Source# 0+ 28.78y - 100% 546 keV 90 Sr - 0.0115% 519.39 keV 2- 64.0h 90 Y 0+ 1760.7 Total measured activity A0 = (71 +/- 6.4) Bq ( accuracy = 9% ) For the moment of the NEMO3 exposition the expected source activity (T=1.12y, T1/2=28.78y) A = A0 . exp (-T . ln2 / T1/2) = ( 69.1 +/- 6.2 ) Bq E0 - 99.9885% 2280.1 keV 0+ 0.0 90 Zr 18-Sep-18 Ref: V. I Tretyak, Aussois, December 05 Shiva King, UCL

90Sr Calibration Runs For the electrons I used the same cuts for the 1e analysis run time: 39448s (Victor Tretyak Aussois 05) 90Y activity: 66.74 +- 0.07(stat) Bq 90Y activity: 65.29 +- 0.11(stat) Bq 18-Sep-18 Shiva King, UCL

90Sr Calibration Runs 18-Sep-18 Shiva King, UCL

90Sr Calibration Runs 18-Sep-18 Shiva King, UCL

Justification of Energy cuts: Phase 1 Which criteria should we use to justify the 2 electron energy cut at 1.5MeV? halflife vs Eee Reduced Chi Square vs Eee signal/sqrt(background) - simple significance vs Eee data vs Eee 18-Sep-18 Shiva King, UCL

Justification of Energy cuts: Phase 1 None of the plots shown here give any justification. Vladimir has suggested to use the following argument: we want systematic bg error < statistical error. We need a cut where 1/sqrt(Ndata) > bgErrorFactor/(s/bg) A cut at 1.6 MeV fulfils this criteria. Alternatively we could justify the 1.5 MeV cut by saying we understand the background well beyond 1.5 MeV and want to maximise statistics. 18-Sep-18 Shiva King, UCL

Cos cuts: Phase 1 18-Sep-18 Shiva King, UCL

48Ca Analysis: Phase 1 18-Sep-18 Shiva King, UCL

18-Sep-18 Shiva King, UCL

90Sr Calibration Runs Exp time: 39448s Victor Tretyak Aussois 05 2174210 696404 1276590 201216 Number of triggers 39448 12613 23205 3630 Corrected time, sec 871558 1703 13799 3232 2725861 43210 Total 1603461 - 25424 3230 250842 1774 3987 3229 Expected 90Sr decays Dead time, s / event Expositon time, s Run# Exp time: 39448s Victor Tretyak Aussois 05 For the electrons I used the same cuts for the 1e analysis For gammas: Internal probabillity > 4% External probability < 1% 18-Sep-18 Shiva King, UCL