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

2. 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 = h; 1.48 y
Run List as suggested by analysis team
18-Sep-18
Shiva King, UCL

3. 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

4. Y90 Activity Measurement: Phase 1 (Paris 2007)
Y90 activity: x10-5(stat) Bq; (stat) mBq/Kg
18-Sep-18
Shiva King, UCL

5. Y90 Activity Measurement: Phase 1
90Y activity: (stat) Bq; (stat) mBq/Kg
210Bi activity: 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

6. Y90 Activity Measurement: Phase 2
90Y activity: e-5(stat) Bq; (stat) mBq/Kg
210Bi activity: Bq
18-Sep-18
Shiva King, UCL

7. 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

8. 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

9. 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

10. 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 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# y
 %
546 keV
90 Sr
 %
keV h
90 Y
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) = ( /- 6.2 ) Bq E0
 %
keV
90 Zr
18-Sep-18
Ref: V. I Tretyak, Aussois, December 05
Shiva King, UCL

11. 90Sr Calibration Runs
For the electrons I used the same cuts for the 1e analysis
run time: 39448s (Victor Tretyak Aussois 05)
90Y activity: (stat) Bq
90Y activity: (stat) Bq
18-Sep-18
Shiva King, UCL

12. 90Sr Calibration Runs
18-Sep-18
Shiva King, UCL

13. 90Sr Calibration Runs
18-Sep-18
Shiva King, UCL

14. 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

15. 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

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

17. 48Ca Analysis: Phase 1
18-Sep-18
Shiva King, UCL

18. 18-Sep-18
Shiva King, UCL

19. 90Sr Calibration Runs Exp time: 39448s Victor Tretyak Aussois 05
696404
201216
Number of triggers
39448
12613
23205
3630
Corrected time, sec
871558
1703
13799
3232
43210
Total -
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