2 Decay of 150Nd, Preliminary Results
(PhaseI data)
Nasim Fatemi-Ghomi
Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
1
Introduction
Background study of 150Nd2
• A study of the 207Bi and 214Bi background in the e-channel.
• A study of the 210Bi, 207Tl+211Pb and 234mPa background in the
e-channel.
• Cross check external background with Cu foil.
Extraction of half-life of 150Nd2
Data Selection
• Good betabeta runs between 2019-3395 (phase I).
• Data taking time =2.8836 x 107s = 0.91 yrs.
• Events should come from Nd2O3. The foil has 57g mass
(37g pure 150Nd).
Analysis tool
Used UCL OO framework written by V.Vasiliev.
Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
2
207Bi
and 214Bi Background Studies
Pre-Selection Cuts for e-channel:
• One negatively charged track
associated with an isolated PMT
Ee > 0.2 MeV.
• Only one  cluster with E> 0.2MeV.
No other  with E> 0.15MeV.
• Internal TOF hypothesis for e events > 5%
• External hypothesis < 1%.
cos(e) < 0.9
• Tracks must have one hit in one of the two first
layers of GG.
Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
3
Activity of 207Bi
In addition to the pre-selection criteria described there should not be any single or
group delayed hit(s) in the tracker.
Fit 207Bi with the data minus background
Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
4
Look at the energy region 0.7 MeV< Ee <1.1 MeV and 0.25 MeV< E <0.6 MeV
where 207Bi dominated over all other backgrounds.
A207Bi=13.4 ± 0.3 mBq ~ 235 ± 5 mBq/kg
Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
5
Activity of 214Bi
Find the activity looking at events with an  (delayed or single hits.)
A214Bi = 0.87  0.17 mBq ~ 15.26  2.98 mBq/kg
Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
6
Find the activity using all the events:
A214Bi = 0.86  0.06 mBq ~ 15  1 mBq/kg
Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
7
1e Channel
Selection cuts:
• One track with negative charge associated with isolated PMT.
• Track has to have a reconstructed vertex.
• Ee > 0.5 MeV.
• Track has to have a hit in one of the first two layers of GG.
mBq
210Bi
21.0  0.3
207Tl
9.29  0.15
211Pb
9.29  0.15
234mPa
4.81 0.05
Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
8
External background
The external background activity found by V.Vasiliev is checked with
looking at the energy distribution of the energy of e-  events coming from
the Cu foil.
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Data = 35524±188, Total Background=34251± 382
Data-Background= 1273 ± 425 -> has to be added to the
systematic uncertainty.
Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
9
Internal Background
Bg
Act(mBq/kg)
Ge measurement
Modane-Baksan
210Bi
368.42
-
207Tl
163.0
-
211Pb
163.0
-
234mPa
84.4
-
Found from e
Channel slide 6
207Bi
235
128 - 120
Found from e +
Slide 7
214Bi
15.3
V.Tretyak(Aussoi
s 2005)
40K
66.7
V.Vasiliev
(Dubna 2004)
208Tl
7.95
9.6 - 5
228Ac
22.1
20 - 15
212Bi
22.1
-
152Eu
38.3(modane)
21.6(Baksan)
Found from 1e
channel slide 8
Ge
measurement
External Background &
Background on the Surface
of the Wires and Foils.
Bg
Act(Bq)
SW 214Bi
0.623
SW 214Pb
0.623
SF 214Bi
0.0185
SF 214Pb
0.0185
PM 214Bi
374
< 3 - 20
PM 214Pb
374
< 6.6 - 9.6
PM 228Ac
515
PM 60Co
50.7
PM 40K
954
Air 214Pb
702
Air 214Bi
702
Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
Found by
V.Vasilev
checked
with Cu foil
Slide 9
10
150Nd
Half-life
Pre-selection for 150Nd to 2 events:
• Two negatively charged tracks associated with isolated PMTs and
E1 ,E2 > 0.2 MeV.
• Both electrons originate from a common vertex
with |∆r| < 2 cm & |∆z| < 4 cm.
• Internal TOF hypothesis > 4% & external TOF hypothesis < 1%.
• Track starts from layers 1 & 2 of GG.
• No delayed alpha decay with refiring time > 70 s.
• No single or group delayed hit(s).
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
11
Results
Number of data events:
1011
Number of total background:
315
Efficiency =133643/2000000
6.68%
T12= 9.04
+0.63(stat)
-0.57
 0.51 (act)  0.78 (syst) x 1018 y
Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
12
Summary
• Looked at e-, e--, and 1e channels to find the activities of
contaminants in the 150Nd foil.
• Looked at e- channel in Cu to cross check the external, surface of
the wire and surface of the foil backgrounds.
• Extraction of the half-life.
• Have to start working with Phase II Data!!
Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
13