1. On behalf of TEXONO collaboration
Study of Neutrino-Electron Scattering with CsI(Tl) Scintillating Crystal Detector
Muhammed Deniz1,2 1: METU, Ankara, Turkey 2: IoP, Academia Sinica, Taiwan
On behalf of TEXONO collaboration
@ 2006 Workshop on the Underground Experiment –
Extension of KIMS + TEXONO Collaboration
TEXONO Physics Program on CsI(Tl) Detector
Shielding and CsI(Tl) Detector Design
Data Analysis Techniques
Cut Summary
Background Understanding and Suppression
Status and Plans

2. TEXONO Physics Program on CsI(Tl) detector
CsI(Tl) (186 kg) :
attempt a measurement of Standard Model (ee-)
 sinw at MeV range
e + e e + e-
Region of Interest for e -ve scattering
Uncertainties in the low energy part of reactor neutrino for SMee  higher energies (T>2 MeV)

3. KS Expt. : Detector Configuration
16 ch, 20 MHz, 8 bit

4. CsI(Tl) crystal layout (93 cry. 186 kg)
100 52 03 12 37 02 04 06 98 22 97 82 71 56 60 90 14 38 20 69 44 47 48 15 99 39 08 89 31 68 78 81 17 34 41 40 46 33 66 92 83 10 35 16 64 49 80 50 43 05 11 23 19 63 32 94 45 27 21 13
220 93 67 53 55 59 24 25
101 26 65 61 62 58 96 42 87 51 73 74 75 76 57 54 86 85 77 72 70 79 91 88 95
Plastic
20+20 cm-veto crys.
40 cm-veto crys.
40 cm-target crys.

5. CsI(Tl) Array : Highlights
Period II Data Volume : Total ~ 110 / 50 days ON/OFF
186 kg mass ; and 40 cm length (longest commercial prod.) CsI(Tl) crystals
Detector Threshold: 3 MeV
Energy: total light collection
z-position: the variation of the ratio
Energy & Z-position info:
 10% 660 keV
Z-position resolution is
(z) = keV
 (z) <2 cm @ higher energies

6. Data Analysing Techniques - Defining Cuts
Alpha Event Pulse
Normal Event Pulse
Alpha Event Cut
having fast decay time
Checking: Alphas are located around 2 MeV
Selection: Mean Time Method: tav vs. q and Double Charge Method: compare total charge with partial charge

7. Data Analysis Techniques - Defining Cuts
40 cm long crystal No cut
b) Z-position Cut:
Definition:
Selection: Both side peak means initially taken as 0 & 40.
Cut: 4 cm from both sides
Narrow Pulse
Normal Pulse
0 cm cm

8. Data Analysis Techniques - Defining Cuts
Veto cut: Reject Cosmic ray Single-hit cut: Anti Compton effect PSD cut : Alpha particle Z-pos cut : Both veto and S.H. effect

9. Data Analysis Techniques - Calibration
1) Z-POSITION CORRECTION:
2) SLOPE CORRECTION:
AFTER CORRECTION
BEFORE CORRECTION
BEFORE CORRECTION
AFTER CORRECTION
3) ENERGY CORRECTION:

10. ON and OFF Energy Spectra
* 37 Crystals (40 cm)
* Mass 59.2 kg
* Basic cuts + Alpha cut + 4 cm Z-cut
ON&OFF spectra in 3-8 MeV
energy range
ON spectrum /day/kg in Period II
OFF spectrum in all energy range
208Tl (2614keV)
40K (1460 keV)
137Cs (662 keV)
OFF spectrum /day/kg in Period II

11. Background Understanding
Two Type :
Radioactive Contaminants
[ Decays of radioactive contaminants mainly 232Th
and 238U chain produce background in the region of interest.
Estimate the abundance of 137Cs, 238U and 232Th inside the detector.
Figure out the contribution of 238U and 232Th chains to the background.
2. Environmental Background
[ Cosmic Ray muons, Products of cosmic ray muons, Spallation neutrons and some radioactive elements like 60Co, 208Tl
Estimate the background related to cosmic rays due to inefficiency a suppression.
Understand and suppress the contribution of 208Tl to the background in region of 3-4 MeV.

12. Background Understanding
Radioactive Contaminants
IDEA: By monitoring the timing and position information related β-α or α-α events can provide distinct signature to identify the decay process and the consistency of the isotopes involved.
Environmental Backgrounds
IDEA: multiple-hit analysis can give us very good understanding especially Tl-208 and cosmic related background in the region of interest
cosmic
By comparing cosmic and not-cosmic multiple-hit spectra.
By examining the pair-production phenomena in not-cosmic multiple-hit spectra.
Tl-208
By examining multiple-hit spectra as well as simulation of Tl-208 decay chain energies to understand/suppress background in the region of 3-4 MeV.

13. Intrinsic 137Cs Level
31.3 kg-day of CsI(Tl) data was analysed.
137Cs contamination level in CsI was drived ==> (1.55 ± 0.02 ) X g/g

14. Intrinsic U and Th Contamination Level
Data: The total of 40 crystals with data size of 1725 kg·day was analyzed.
Master Thesis results of Zhu Y. F. from Tsing Hua Univ. in Beijing (2006)
ii) 212Bi(b-,64%) → 212Po(a, 299ns) → 208Pb
i) 214Bi(b-)→ 214Po(a,164ms) → 210Pb
Selection: b- pulse followed by a large a pulse
Selection: 1st pulse is g(b) shaped &
2nd pulse a shaped
T1/2 = (283 ± 37) ns. β α β α
T1/2 = (163 ±8) ms
232Th abundance = 2.3 ± 0.1 x10-12 g/g
238U abundance = 0.82 ± 0.02 x g/g
T1/2 = (0.141± 0.006) s a
iii) 220Rn(a) → 216Po(a, 0.15s) → 212Pb
Selection: two α events with time delay less than 1s
232Th abundance = 2.23 ± 0.06 x g/g

15. Background Understanding via Multi Hit
The Sources are external
510
1170
1330
2100
600
800
Co-60 contamination
keV 99.86% accompanied with keV 99.98%
Tl Pair Production: One escape peaks
(~ keV)
Cs-134 (n + 133Cs g 134Cs)
97.6% 605 keV;
85.5% 796 keV
The Source is external
2614 keV % accompanied with
583 keV 86%
510.8 keV 22.6%
860 keV with 12.4%
The source is internal.
Cosmic induced neutrons can be captured by the target nuclei 133Cs.
Combination of Tl gammas can affect up to around 4 MeV

16. Background Understanding – Tl-208 and Cosmic Inefficiency

17. Study on Background in Statistically
To understand the contribution of cosmic rays to the background,
~ 926 kg*day data was analyzed for cosmic and not-cosmic multi-hit as well as pair production.
2&3 Hit Approach for 4 – 8 MeV
Two-Hit:
Expected to Single-Hit ratio:
Exp/SH = cm z-cut
= 0.96 for no z-cut
Three-Hit:
Exp/SH = 0.98 for 4cm z-cut
= 1.15 for no z-cut
Pair Production Approach for 4 – 8 MeV
For no z-cut
Exp/SH = 1.03
For 4cm z-cut
Exp/SH = 0.90

18. c 2 Analysis
There are two kinds of background events within our signal.
one is matching well with reference g-pulse (b-)and
the other is fast- falling (a)…
Black – Recorded Pulse by FADC
Green – Reference a pulse
Red - Reference g pulse
TYPE I
TYPE II
Left side
Right side
Left side
Right side ○ ○

19. Cutting at this point, suppression 66%(.248/.727)
c 2 Analysis
Cutting at this point, suppression 66%(.248/.727)
c-square function
Red – b events
Black – g events

20. Preliminary Result of sin2qW
Ph.D. Thesis results of Dr. Lin Shin Ted (2006) g
The best fit of sin2qW : ± at 3-8MeV
0.30 ± at 3.5-8MeV

21. Expected Accuracy of sin2qW with data size
130

22. Expected Result of Accuracy of e-e) and sin2qW

23. “Our aim is to measure (ee) with <20% accuracy.”
TEXONO and World status !
Characteristics of the previous and current neutrino-e scattering experiments
CsI(Tl) cry.
186 kg
3.0
1.8 (expect)
0.1
<20% (goal)
CF4 gas
21 kg
0.9
1.77
0.2
50%
Si(Li)
37.5 kg
0.6
5.2
0.008
49%
Fluorocarbon
103 kg
3.1
0.78
53%
Plastic scin.
15.9 kg
1.5
1.2
0.18
29%*
TEXONO
NUMU
Rovno
Kurtchatov
Savannah
Experiments
Target
Fiducial Mass
Thr. (MeV)
Signal Evt./Day
S / B
Accuracy of
(ee)
“Our aim is to measure (ee) with <20% accuracy.”
Our aim is to measure Sin2W value with <8% accuracy.

24. Thank you