1. (On behalf of the TEXONO Collaboration) Academia Sinica, Taiwan
Study of neutrino-electron scattering with CsI(Tl) crystal array at Kuo-Sheng Reactor Laboratory
Lin Shin-Ted
(On behalf of the TEXONO Collaboration) Academia Sinica, Taiwan
@NSYSU Feb. 2005
Physics with neutrino-electron interaction
Period -II configuration on CsI(Tl) detector
Data Analysis Techniques
※ Cuts ※ Cut summary
Background Understanding (ZYF’s input)
Results (Prelim.)
Taiwan EXperiement On NeutrinO

2. g g g
For (ne-e), both NC & CC and their interference term contribute

3. Reactor Neutrino Interaction Cross-Sections
Reactor : high flux of low (MeV range) energy ne
On-Going Data Taking: 4SM s (ne) 4T > 3 MeV
R&D: 4Coh. (nN) 4T< 1 keV
Results & More Data: mn (ne) 4T~ keV

4. Kuo-Sheng Reactor Neutrino Laboratory
Front Gate
Front View (cosmic vetos, shieldings, control room …..)
Configuration: Modest yet Unique
Flexible Design: Allows different detectors conf. for different physics
Inner Target Volume

5. Period-2 CsI(Tl) Array : 186 kg, 93 crystals
Period II : Jan.28, 2003 – Jan ( ~ 50 days OFF 130 days ON)
Single Crystal QL Vs QR (Raw Data)
Z = 0 cm
Z =40 cm
208Tl
40K
137Cs
Region of Interest for SM s(ne)

6. CsI(Tl) Array : Highlights
40 cm length; 186 kg mass
(longest commercial prod.)
Energy+3D info:
 10% 660 keV
Z-position resolution is keV
 s(z) <2 cm @ E>250 keV
Detector Threshold 3 MeV
Range of O ( cpd) [counts/kg/day] > 3 MeV background
PSD for g/a : > 99%
Data Volume : Total > 250 / 50 days ON/OFF
Goals:
Commission 500 kg target on-site
DAQ with large dynamic range

7. Data Analysis Techniques
No Cut: Energy Spectrum
Defining Cuts:
1] General Cuts – a) No Cut energy spectrum b) Single Event Hit & Single Crystal Hit c) Cosmic ray Cut
d) Rough Z-pos. cut
SEH, SCH
SEH, & SCH
SEH, SCH, & Cosmic
SEH, SCH, Cosmic-ray, & Z-pos
SEH, SCH
SEH, SCH
SEH, SCH

8. Data Analysis Techniques
Defining Cuts: 2] Special Cuts –
a) Alpha Event Cut (having fast decay time)
Check-Alphas are
located around 2 MeV
Select-event having
Time average less
than 40
[Nucl. Instrum. Methods A 523, 116 (2004)]
Normal Event Pulse
Alpha Event Pulse
A; .

9. Data Analysis Techniques
Defining Cuts: 3] Special Cuts –
a) Double Event Cut (Left side double pulse) b – a pulse !
232Th series:
212Bi(β-, 60.6min, 64%) → 212Po(α, 304ns) → 208Pb

10. Data Analysis Techniques
Defining Cuts: 4] Special Cuts –
a) Double Event Cut (Right side Double Pulse)

11. Data Analysis Techniques
40cm long crystal No cut
Defining Cuts: 3] Z-position Cut –
Select – Both side peak mean initially taken as 0 & 40 !
0 cm cm
Narrow Pulse
Normal Pulse
Alpha Pulse

12. Cut Summary
Cut Type All energy Above 3 MeV Efficiency (Suppression) (Suppression) [1] Raw data [2] Cosmic ray [3] anti-Compton [4] Single Trigger [5] Alpha [6] Double Pulse (Left side & Right side)
* Z-position cut is not applied !!

13. Period-II CsI(Tl) Array : Results (Prilim.) OFF/ON DATA
Energy Spectrum of recoil electron
137Cs (661 keV)
137Cs (661 keV)
40K (1461 keV)
40K (1461 keV)
208Tl (2615 keV)
208Tl (2615 keV)

14. Background Understanding
Prospects:-
Estimate the abundance of 238U and 232Th
Figure out the contribution of the two chains to the spectrum of the background

15. 232Th Decay chain α- α events Selection:
Simply choose α events and inspect the time interval between two adjacent ones
Cuts:Cosmic ray veto,
Single hit, delay time<1s
220Rn --(55.6 s Ea=6.405MeV)->
216Po --(0.145 s Ea=6.907MeV->
212Pb
Results:
Delaytime
T1/2=0.153 sec.
Energy:
6.405MeV: KeV
QF: 1.87
6.907MeV: KeV
QF: 1.83

16. Background Understanding
From tagging event by event
beta-alpha rate /day/kg
alpha-alpha rate /day/kg
Results:
Above 3 MeV
/day/kg
Above 3.5 MeV
/day/kg
- delayed coincidence

17. Results (Prilim.) OFF DATA(~3000 kg.days)
Energy Spectrum of recoil electron
137Cs (661 keV)
Above 3 MeV
Counts/day/kg = (SM)
Counts/day/kg =
Above 3.5 MeV
Counts/day/kg = (SM)
Counts/day/kg =
40K (1461 keV)
208Tl (2615 keV)
4 cm zpos (both side) cut !!
* 42 Crystals (40 cm.)
* Mass 67.2 kg
* Data set 46 days OFF period

18. Period-II CsI(Tl) Array : Results (Prelim.)
The Estimate of BKG Suppression >3 MeV
* Cosmic ~ one order
* From Veto to All Cuts > Two order
* 80kg All Cuts to ON-OFF ~ One order
* S/B ratio (integral > 3 MeV) = 1/ 2.8 (->2.4)
* D = (ds/s) = 40 % ~ 2.3s measurement !
10500 kg-days ON-period 3200 kg-days OFF-period
Differential Event Count for CsI(Tl)

19. World status !
General conclusion is that a 1% measurement is well-worth pursuing !
“There is NOT YET any real measurement of reactor neutrino expt”.
TEXONO
Qw(Cs)
NuTeV
Czarnecki & Marciano (2000)
E158 Run I+II (Preliminary)
PDG2002
Measurements of sin2qw as a function of Q. The curve shows
the Standard Model expectation

20. Expected Sensitivities :
World status !
Experiments
Savannah
Kurtchatov
Rovno
NUMU
TEXONO
Target
Fid. Mass
Thr. (MeV)
Signal Evt. / D
S / B
Accuracy of
s(nee)
Plastic scin.
15.9 kg
1.5
1.2
0.18
29%*
Fluorocarbon
103 kg
3.1
0.78
0.1
53%
Si(Li)
37.5 kg
0.6
5.2
0.008
49%
CF4 gas
21 kg
0.9
1.77
0.2
50%
CsI(Tl) cry.
84 kg
3.0
1.1 (expect)
0.4 (current)
43% (current)
20% (goal)
Characteristics of the previous and current neutrino-e scattering experiments
Expected Sensitivities :
The accuracy of s(nee) drop down to 20%
“Sin2qW was observed but there is NOT YET any real measurement for reactor neutrino”.