Status of the Measurement of AntiNeutrino-Electron Scattering In

TEXONO Experiment Muhammed Deniz1,2

1: METU, Ankara, Turkey2: IoP, Academia Sinica,

Taiwan

2nd Korea-China Joint Seminar on Dark

Matter Search @ SNU

Outline

Neutrino-Electron Scattering

Highlights on CsI(Tl) Detector

Shielding and CsI(Tl) Detector Design

CsI(Tl) Detector Array

Event Selection Criteria and Cut Summary

Multi-Hit and Pair-Production Analysis

Single Hit Background Predictions

Future Plans and Conclusion

Theory

TEXONO Experiment

Data Analysing Techniques

Background Understanding and Suppression Methods

Status and Results

TEXONO Physics Program

Neutrino-Electron Scattering Cross-Section

e + e- e + e-

e + e- e + e-

Neutrino-Electron Scattering Cross-Section

MeVin

kgdaycpd

83

)( 0123205.0 11

PDG table

sin2W measurement in the World

“There is NO significant measurement at low energies especially with reactor anti-neutrino”

PDG 2007

TEXONO Physics Program on CsI(Tl) detector

• attempt a measurement of Standard Model ee

sin2w at MeV range

Measurement : Recoil Energy of e

• attempt a measurement of Standard Model ee

sin2w at MeV range

Measurement : Recoil Energy of e

e + e- e + e-

Reactor : high flux of low energy (MeV range) electron anti-neutrinos.

properties are not fully understood intense -source

• Region of Interest for e - e scattering

Big uncertainties of modeling in the low energy part of reactor neutrino for SM (ee) higher energies (T>3 MeV)

• Region of Interest for e - e scattering

Big uncertainties of modeling in the low energy part of reactor neutrino for SM (ee) higher energies (T>3 MeV)

CsI(Tl) (200 kg) : CsI(Tl) (200 kg) :

Kuo-Sheng Reactor Neutrino Laboratory Front Gate Inner Target Volume & Shielding

Front View (cosmic vetos, shieldings, control room …..)

Control Room

CsI(Tl) Detector

Detector Configuration

KS CsI(Tl) Experiment Configuration

Multi-Disks Array (several Tb)

CsI(Tl) (200 kg) Connecting Board

FADC Readout

16 ch., 20 MHz, 8 bit

Period II Data Volume (186 kg in mass):

Total ~95 / 50 days ON/OFF

Period III Data Volume (200 kg in mass):

Total ~190 / 40 days ON/OFF

Detector Threshold: 3 MeV

Energy: total light collection

Detector Threshold: 3 MeV

Energy: total light collection

RL~ QQE

z-position: the variation of the ratioz-position: the variation of the ratio

)/()( RLRL QQQQZ

Energy resolution info:

10% FWHM @ 660 keV

Z-position resolution is

(z) = 2 cm @ 660 keV

(z) <2 cm @ higher energies

Energy resolution info:

10% FWHM @ 660 keV

Z-position resolution is

(z) = 2 cm @ 660 keV

(z) <2 cm @ higher energies

CsI(Tl) Array : Highlights

Z position cut

from both sides 4 cm cut is applied to the 40 cm length

crystals.

Pulse Shape Discrimination (PSD)

separate different pulse shapes from real signal.

Single-Hit (SH)select only one hit and only one

crystal fired at one time.

Cosmic Ray Veto (CRV)

record the time gap between the last hit of veto and trigger

signal.

Event Selection

Alpha Event Pulse

Normal Event Pulse

Data Analysing Techniques - Defining Cuts

having fast decay time

Checking: Alphas are located around 2.5 MeV

Selection:

Mean Time Method: tav vs. q and

Double Charge Method: compare total charge with partial charge

Alpha Cut

Data Analysing Techniques - Defining Cuts

Left side double pulse ( – pulse)A

Right side Double PulseB

PSD Cut : Double EventPSD Cut : Double Event

P-II and P-III OFF CsI Energy Spectra with Various Cuts

The Efficiency and Suppression Factors of Various Cuts

CUTS

(3 - 8 MeV)

Suppression(cpd)

raw 245.935

Efficiencies

Live Time Eff.

93.53%

CRV28.824

(11.72 %) 94.04%

SH3.103

(10.76 %) 99.66%

PSD1.532

(49.37 %) ~100%

Z-Cut0.5234

(34.16%) 80%

Total 0.213 % 74.98 %

CUTS

(3 - 8 MeV)

Suppression(cpd)

raw 415.239

Efficiencies

Live Time Eff.

88.78%

CRV26.672

(6.42 %)92.67 %

SH3.682

(15.64 %)99.91 %

PSD1.235

(33.54 %)~100 %

Z-Cut0.447

(36.19 %)80%

Total 0.107 % 77.07 %

Period-IIPeriod-II Period-IIIPeriod-III

The Stability Check

0.2 % 0.17 %

Period - II Period - III

0.87 % 0.80 %

Cut EfficiencyCut Efficiency Cut EfficiencyCut Efficiency

Data StabiltyData Stabilty Data StabiltyData Stabilty

Period - II Period - III

The Stability Check 3-8 MeV

OFF ONOFF ON

P-II & P-III CsI Energy Spectra

OFF P-II and P-III ON P-II and P-III

Decays of radioactive contaminants mainly 232Th and 238U decay chain produce background in the region of interest. Estimate the abundance of 137Cs, 238U and 232Th inside the detector.

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.

A. Radioactive Contaminants

Background Understanding

Cosmic Ray muons, Products of cosmic ray muons, Spallation neutrons and some radioactive elements like 60Co, 208Tl

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.

- 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.

B. Environmental Backgrounds

Efficiencies, Measured Half-Livesand Contamination Level

Published Zhu Y. F., et al., Nucl. Instr. and Meth. A 557 (2006) 490-500.

137Cs contamination level in CsI ==> (1.55 ± 0.02 ) X 10-17 g/g

BR 36%

This can be negligible background in our background level of ~ 0.4 cpd in 3 - 5 MeV

208Tl beta with associated gammas energies deposit in one crystal.

208Tl beta with associated gammas energies deposit in one crystal.

Estimate the background due to Intrinsic 208Tl

232Th (decay chain)

3a, 3b

Environmental Background Understanding

Tl-208 (3-4 MeV) 208Tl chain 2-hit energy spectra

Simulation with angular correlation

taking cosmic/non-cosmic ratio for 2&3-hit energy spectra

Pair production cosmic/non-cosmic ratio for 3-hit

Cosmic Inefficiency

Nearly all crystals including 20+20 and 40 cm crystals data was analyzed.

Background Understanding via Multi Hit511 keV

1173 keV 1332 keV

2100 keV

External Source(s)

• Co-60

• 1173.2 keV 99.86% accompanied with 1332.5 keV 99.98%

• The background related to reactor. Mostly come from the dust.

• Tl Pair Production: One escape peaks

• (~ 2105 + 511 keV)

Internal Source(s)

Cosmic induced neutrons can be captured by the target nuclei 133Cs.

Cs-134 (n + 133Cs 134Cs)

• 605 keV 97.6%;

• 796 keV 85.5%

With the Q of beta decay at 2MeV

Combination of Tl gammas can affect up to around 4 MeV

External Source(s)

2614 keV 99 % accompanied with

583 keV 85%

510.8 keV 23%

860 keV with 13%

510, 583 keV

860 keV

2614 keV

605 keV

796 keV

Etot = 1-2 MeV Etot = 2-3 MeV

Etot = 3-4 MeV

Background Understanding: Due to Tl-208 and Cosmic Inefficiency

Background Understanding: Due to Tl-208

Tl-208 SH Estimation 3 - 3.5 MeV PIII-ON Period

Best fit = 0.0444 ± 0.00407

= 8.59/(nof=8) SH = 610.38 ± 55.90

No z-cut 4 cm z-cut583 keV + 2614 keV

where T1 = (SH)not cos + (SH)cos and

T2 = (MH)not cos + (MH)cos

SH Background Prediction Due to Cosmic

= ON - OFF

= ON - (SH)pred.

= ON - OFF

= ON - (SH)pred.

SH)pred < OFF we win with this alternative approach …

Single Hit Prediction is made by using ON period data. We can improve

accuracy profoundly since we have more than 100 days ON data in PII and 200

days in PIII and more for other periods …

ON

pred

ON T

SH

T

MHnon

)1

(1)2

(cos

= ON - BKG = ON - BKG

E e-e+

E e-e+

E e-e+

Background Expectation via PAIR PRODUCTION

3 - HIT2 - HIT

SH

p

q

p

p

q

q

Background Understanding via Multi-Hit

Period-III

cosmic

3.0 – 3.5

Tl-208/Cu

Reactor OFF

Energy (MeV) Tl-208/Cu

~ 100

47 %

Period

3.5 – 6.5

Period - IIIPeriod - II

6.5 – 8.0

~ 100

46 %

-

54 % Cu

-

53 % Cu

cosmic

63 % 46 % 54 % Tl 37 % Tl

Period-II

SH Prediction via Multi-Hit for OFF DataPeriod - II Period - IIIOFF-(SH)pred.

SH Prediction via Multi-Hit for ON Data

961 ± 31

3.5 – 4.0

1721.2 ±63.9

Period-II Period-III

3.0 – 3.5 963 ± 31 921.6 ± 42.1

158 ± 12.5

173 ± 13.2

261 ± 16.2

516 ± 22.7

349 ± 18.7

202 ± 14.3

194 ±13.9

138 ± 11.7

Energy (MeV)

76 ± 8.7

6.0 – 6.5 55 ± 7.4

5.0 – 5.5 118 ± 10.8

4.0 – 4.5

Single-HitSingle - Hit

4.5 – 5.0

5.5 – 6.0

6.5 – 7.0

7.0 – 7.57.5 – 8.0

194 ± 13.9

141 ± 11.9

81 ± 9

80 ± 8.9

73 ± 8.5

Prediction Prediction

196.3 ± 13.5

133.7 ± 11.1

94.9 ± 9.4

69.1 ± 7.9

52.7 ± 6.9

80.3 ± 8.3

76.7 ± 7.9

61.4 ± 7.1

489.3±20.6

353.8 ±17.5

259.5±15.0

192.5±12.9

176.5±12.1

150.2±11.2

160.6±11.1

134.6 ± 9.9

1762 ± 41.9

724 ± 26.9 292 ± 17.1 282.2 ± 16.2 704.9±24.7

ON-BKG

Sin2W = 0.294 ± 0.0933

sin2W measurement for Period-II

0.08210.1156-W

2 0.294 θsin SMRdR )(exp

ON-BKG

Sin2W = 0.225 ± 0.113

sin2W measurement for Period-III

0.09420.2005-W

2 0.225 θsin SMRdR )(exp

sin2W measurement for Period-II + Period-III

0.06450.0865-W

2 0.259 θsin (ON-BKG)p2+p3

Sin2W = 0.259 ± 0.0724

SMRdR )(exp

TEXONO Status

The Summary of cross section and Weinberg Angle

Measurements with various methods

R = (1.258 ± 0.7691) RR = (1.258 ± 0.7691) RSMSM

SinSin22WW = 0.275 ± 0.101 = 0.275 ± 0.101

R = (0.911 ± 0.707) RR = (0.911 ± 0.707) RSMSM

SinSin22WW = 0.225 ± 0.113 = 0.225 ± 0.113

R = (0.942 ± 0.9169) RR = (0.942 ± 0.9169) RSMSM

SinSin22WW = 0.229 ± 0.144 = 0.229 ± 0.144

R = (1.407 ± 0.7556) RR = (1.407 ± 0.7556) RSMSM

SinSin22WW = 0.294 ± 0.0933 = 0.294 ± 0.0933

R = (1.189 ± 1.083) RR = (1.189 ± 1.083) RSMSM

SinSin22WW = 0.266 ± 0.148 = 0.266 ± 0.148

R = (1.614 ± 1.055) RR = (1.614 ± 1.055) RSMSM

SinSin22WW = 0.319 ± 0.120 = 0.319 ± 0.120

R = (0.8662 ± 1.111) RR = (0.8662 ± 1.111) RSMSM

SinSin22WW = 0.218 ± 0.184 = 0.218 ± 0.184

ON – SHpred

ON – BKG

R = (1.044 ± 0.7011) RR = (1.044 ± 0.7011) RSMSM

SinSin22WW = 0.245 ± 0.103 = 0.245 ± 0.103

R = (1.141 ± 0.5181) RR = (1.141 ± 0.5181) RSMSM

SinSin22WW = 0.259 ± 0.0724 = 0.259 ± 0.0724

Period – IIIPeriod – III Period – II + IIIPeriod – II + IIIMethods Period – IIPeriod – II

ON – OFF

e- Scattering Cross-Section and

sin2W measurement in the world

e-

e-

R = (1.141 ± 0.5181) RR = (1.141 ± 0.5181) RSMSM

SinSin22WW = 0.259 ± 0.0724 = 0.259 ± 0.0724TEXONO

Expected Accuracy with data size

For . sin2W For . cross-section

28%

19%

15%

45%

32%

26%

(%) = 0.60 e(%)W

2sin

Status of P-IV Data – Very Preliminary

ON P-IV

Neutrino-Electron Scattering Cross-Section

The Interferece Term

9/90.13 744.0917.0 2exp I

SMI RR

ISM

NCCCI RRRRR expexpNCCCI

SM

“Our aim is to measure eee) e) with < 15% < 15% accuracy”.

“Our aim is to measure sin2W value with < 10% accuracy”.

For this purpose

get more stable and in good condition data

understand the background further and develop suppression

methods effectively.

“Our aim is to measure eee) e) with < 15% < 15% accuracy”.

“Our aim is to measure sin2W value with < 10% accuracy”.

For this purpose

get more stable and in good condition data

understand the background further and develop suppression

methods effectively.

Conclusion

“This will be the first significant results in the measurement of eee),e),Interference eee) term e) term and sin2W value at low energy with reactor neutrino”.

“This will be the first significant results in the measurement of eee),e),Interference eee) term e) term and sin2W value at low energy with reactor neutrino”.

Thank you