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Performance and Physics with the CsI(Tl) Array at the Kuo-Sheng Reactor Neutrino Laboratory

Physics with CsI(Tl) detector

Period -2 configuration

Data analysis

※ Cuts

※ Cut summary (central crystals)

Results (Prilim.)

Background

Status and plans

Summary

V. Singh(On behalf of the TEXONO Collaboration)

IoP, Academia Sinica, Taipei, Taiwan

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Physics with CsI(Tl) detcetor

physics full of surprises , need intense -source

Reactor : high flux of low (MeV range) energy electron anti-neutrinos e + p e+ + n

Reactor -spectrum has been measured (~2% in the 3 - 7 MeV)For (e-e), both NC & CC and their interference term contribute

g

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Physics with CsI(Tl) detcetor

Investigations of (e-e) cross-sections with reactor s

To study : Electro-weak parameters (gv, gA, Sin2W) at

the MeV range CC & NC interference anomalous magnetic moments and mean square charge radius

NCEX on nuclei by e + (A,Z) e + (A,Z)*

NOT observed at lower energies !

CsI(Tl) have good resolution and capture efficiency & suitable to study these processes.

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KS Expt. : Period II Configuration

Shielding & Veto [one side]

Period II : Jan.28, 2003 – Jan.08 2004 ( ~ 50 days OFF)

CsI(Tl) Array (186 kg)

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KS Expt: Period II CsI(Tl) Detector

CsI(Tl) [ 186 kg ] Connecting Board

Multi-Disks Array [800 Gb]

Flash ADC Readout[16 ch, 20 MHz, 8 bit]

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Reactor Neutrino Interaction Cross-Sections

P3+: Coh. (N) < 1 keV

P1: MM (e) 1-100 keV

P2: SM (e) > 2 MeV

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KS/P-2/CsI(Tl)/Cross-Section Data

Data Volume: Total more than 250 / 50 days ON/OFF

CsI(Tl) Performance: 186 kg mass (Future target 500 kg mass) FWHM energy resolution of 10% @ 660 keV Z-position resolution is 2cm @ 660 keV

Range of O(0.0048 cpd) [counts kg-1 day-1 10keV-1] @ 3 MeV background

Analysis: Cosmic Veto (5 s gate) Anti-Compton (Whole Ge detector assembly + Rest CsI(Tl) crystal

s) Pulse Shape Disc. (Alphas, elect. noise, accidentals etc.)

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95 88 91 79 70 72 77 85

86 54 57 76 75 74 73 51 87

42 96 58 62 61 65 26 101

25 24 59 55 53 67 93 220 13

21 27 45 94 32 63 19 23

11 05 43 50 80 49 64 16 35

10 83 92 66 33 46 40 41

34 17 81 78 68 31 89 08 39

99 15 48 47 44 69 20 38

14 90 60 56 71 82 97 22 98

06 04 02 37 12 03 52 100

CsI(Tl) crystal layout

Plastic 20+20 cm 40 cm 7 central cry. Anal. underway

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Period-2 CsI(Tl) Array : 186 kg, 93 crystals

Single Crystal QL Vs QR (Raw Data)

Region of Interest for SM e)

Z = 0 cm

Z =40 cm

208Tl

40K 137Cs

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Data Analysis Techniques

Defining Cuts:

1] General Cuts –a) No Cut energy spectrumb) Single Event Hit & Single Crystal Hit c) Cosmic ray Cut

SEH, & SCH SEH, SCH, & CosmicSEH, SCH

SEH, SCH, Cosmic-ray, & Z-pos

SEH, SCHSEH, SCHSEH, SCH

No Cut: Energy Spectrum

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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

Data Analysis Techniques

A; .

Alpha Event Pulse

Normal Event Pulse

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Defining Cuts:3] Special Cuts –

b) Very narrow Event Cut (Very fast decay time)

Select- event having partialcharge less than 3

Note- Not in all crystals.

Data Analysis Techniques

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Data Analysis Techniques

Defining Cuts:4] Special Cuts –

c) Double Pulse Cut

Select – Event havingLarger Time Avg.but low charge !

A;

Right side Double Pulse

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Data Analysis Techniques

Defining Cuts:5] Z-position Cut –

Select – Both side peak mean initially taken as 0 & 40 !

40cm long crystal No cut

Narrow Pulse

Alpha Pulse

Normal Pulse

0 cm 40 cm

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Cut Summary of Central Crystals

Cut type Over all energy Above 3 MeV

(%) (%)[1] Cosmic ray 11 88[2] anti-Comp. 70 86[3] Single Tri. 01 02[4] 1+2+3 72 95

[5] Alpha+Narrow 10 83[6] Double Pulse 11 38[7] PSD 25 95[8] All Cuts 32 96

* Z-position cut is not applied !!

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Period-2 CsI(Tl) Array : Results (prilim.)

Energy Spectrum of Alpha and narrow pulse

Narrow Pulse Peak

Alpha Peaks

Z-positon of Alpha

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211 kg-days Energy Spectrum of recoil electron

* 16 Central Crystals

* Mass 32 kg

* Data set 6.9 days OFF period

Period-2 CsI(Tl) Array : Results (Prilim.)

137Cs (661 keV)

40K (1461 keV)

208Tl (2615 keV)

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Period-2 CsI(Tl) Array : Results (Prilim.)

The Estimate of BKG Suppression >3 MeV

* Cosmic ~ one order

* From Veto to All Cuts> Two order

* 100kg All Cuts to ON-OFF ~ One order

* S/B ratio (integral > 3 MeV) = 1/10

Differential Event Count for CsI(Tl)

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BKG in CsI(Tl) detcetor

Internal intrinsic radioactivity: Multi-structure in Alpha spectrum (study is underway)

Concentration of 137Cs = 1/( 2.14 x 10-18 ) g / g

* is more than 0.5

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Attempt measurement of Standard Model (ee-) sinw at MeV rangeAnalysis: [1]

Central 16 crystals gone well To study alpha spectrum Need more attention a) Energy resolution b) Z-position

Rest 15 (40cm) is next step Rest 10 (40cm) and 17 (20cm) is second next step

Future Upgrades and Modifications of the Expt.: Goal of achieving a 500 kg system Improvements of Shielding More Physics Data Taking

To investigate complementary detection technique

To study the other unexplored channels

Status and Plans

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Present Results:

Bkg ~ 10- 3 kg-1day-110 keV-1 at 3 MeVON - OFF ~10- 4 kg-1day-110keV-1at 3 MeV

S/B ratio = 1/10

Summary

After analyzing all crystals and after ON - OFF

Data, we will present better results !

Thanking you for your kind attention !

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Cut Summary of Central Crystals

1 2 3 4 5 6 7 8 9 10

32 88 18 99 16 91 98 94 82 76

80 90 34 99 32 95 84 95 89 74

49 89 27 99 25 97 99 98 82 82

94 90 31 99 28 88 83 86 55 50

50 90 31 99 28 99 86 92 84 72

33 88 13 99 12 96 89 93 80 73

66 91 52 99 47 59 89 61 56 46

78 87 36 99 33 96 87 90 75 68

[01]= Cry. #, [02]= Cosmic, [03]= Single Cry., [04]= Single Tri., [05]=Cos+Sc+St,

[06]= Alpha+Narrow, [07]= Wrong ipos, [08]= Double Pulse, [9]= PSD, [10]= All cuts

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Cut Summary of Central Crystals ( > 3 MeV)

1 2 3 4 5 6 7 8 9 10

32 14 16 98 07 25 93 15 09 08

80 09 11 97 03 14 76 86 10 07

49 13 18 99 06 20 97 32 07 04

94 11 12 98 04 03 73 95 00 00

50 10 11 98 02 44 87 91 09 09

33 16 17 98 08 09 86 18 01 01

66 09 12 97 02 06 77 94 00 00

[01]= Cry. #, [02]= Cosmic, [03]= Single Cry., [04]= Single Tri., [05]=Cos+Sc+St,

[06]= Alpha+Narrow, [07]= Wrong ipos, [08]= Double Pulse, [9]= PSD, [10]= All cuts