WIMPs search project with highly segmented NaI(Tl) scintillators - - PowerPoint PPT Presentation

WIMPs search project with highly segmented NaI(Tl) scintillators

Ken-Ichi Fushimi Faculty of Integrated Arts and Sciences The University of Tokushima

CONTENTS

Signal Selection by Spatial and Time

Correlation

Thin NaI(Tl) plate for WIMPs search Performance of thin NaI(Tl) Plan for Underground Experiment Summary

Collaboration

The University of Tokushima

K.F, H.Kawasuso, M.Toi, K.Yasuda, E.Matsumoto,

E.Aihara, R.Hayami, S.Nakayama, N.Koori

Osaka University

K.Ichihara, S.Umehara, S.Yoshida, M.Nomachi,

H.Nakamura, R.Hazama

ICU

H.Ejiri

WIMPs search by scintillators

Large Mass (~100kg) Good Target Nuclei

23Na for SD (NaI) 127I for SI,SD,EX (NaI, CsI) 19F for SD (CaF2) 129Xe for SD,SI,EX (Xe)

Low Cost

Sensitivity for WIMPs

2

A ∝ σ

) 1 (

2

+ ∝ J J Cλ σ

N N

χ χ

N N J J

SI SD

N J J J’

*

1 1 1 2 1 ' 2 A M A g J J

M

+ + ∝ σ

EX

N

Signal selection by Spatial and Timing Correlation

SSSC analysis Signal Selection by Spatial Correlation

Signal 57.6keV γ + Low energy recoil Localized event Background High energy γ and β Diffused event

SSTC analysis Signal Selection by Time Correlation

Signal Timely localized T1/2=0.9ns (57.6keV excited state) Background Timely correlated

214Bi214Po (T1/2=164µs) 210Pb210Bi(T1/2=5days)

Segmented NaI(Tl) plate for DM search

23Na &127I

Sensitive to SD and SI 100% natural abundance

127I

Sensitive to EX Low energy excited state

Expect: 3.60×10-3/day/kg (Higgsino) Limit: 4.98×10-2/day/kg (ELE V NaI)

57.6keV 7/2 0keV 5/2

127I

Experimentally obtained

1 .

2 1

=

M

M

Previous technique

127I

χ χ

Recoil

γ

dR dE (Arb. Unit)

• 2

2 4 6 8 1 2 4 6 8 1

ENERGY(keV)

Difficult to identify BG and Signal.

Signal identification by segmentation

127I

χ χ γ

• 2

2 4 6 8 1 2 4 6 8 1

E N E R G Y ( k e V )

Recoil

2 4 6 8 1 2 4 6 8 1

E N E R G Y ( k e V )

Estimation of signal selectivity

Monte Carlo simulation (GEANT4) 57.6keV gamma ray from one module γ is detected the another module Next module to the emitter module

The fraction which is detected both sides of emitter

Fraction of detected g by neighboring modules

0.11 1.5mm 0.15 1.0mm 0.18 0.75mm 0.21 0.5mm

Coincidence probability Thickness of NaI(Tl)

0.11 1.5mm 0.15 1.0mm 0.18 0.75mm 0.21 0.5mm

Coincidence probability Thickness of NaI(Tl)

Specification of thin NaI array

0.05cmX5cmX5cm NaI(Tl) 0.05cmX6cmx0.5cm Acrylic Light Guide ESR reflector 16modules (phase 1) 256modules (phase 2) 1024, 2176 (phase 3,4)

MC simulation for BG

Radioactive contamination

Uniformly contaminated in NaI(Tl) crystal 210Pb 0.1mBq/kg (1/100 of present value) 214Pb, 214Bi 10µBq/kg (present value)

Condition of SSSTC

214Pb,214Bi

SSSTC analysis Delayed Coincidence ΔT<1ms Reduction factor=0.03 SSSTC 1s<ΔT<60min (3T1/2) Reduction factor=0.003

210Pb,210Bi

SSSTC analysis Successive β ray in 12.5 days (2.5T1/2) Reduction factor=0.177

Expected BG

1

• 6

1

• 5

. 1 . 1 . 1 . 1 1 5 1 1 5 2 2 5 T O T A L ( S ) / d a y / k g T O T A L ( C ) / d a y / k g

• S

S T C

E V E N T S / d a y / k g E N E R G Y ( k e V )

SINGLES SSSTC

Energy window of analysis

1

• 6

1

• 5

. 1 . 1 . 1 . 1 1 1 2 3 4 5 T O T A L ( S ) / d a y / k g T O T A L ( C ) / d a y / k g

• S

S T C

E V E N T S / d a y / k g E N E R G Y ( k e V )

Coincidence event rate

keV 10 keV 2 ≤ ≤

ee

E

1

• 6

1

• 5

. 1 . 1 . 1 . 1 1 1 2 3 4 5 T O T A L ( S ) / d a y / k g T O T A L ( C ) / d a y / k g

• S

S T C

E V E N T S / d a y / k g E N E R G Y ( k e V )

Upper limit on BG rate

N a I ( T l ) t h i c k n e s s = . 5 U p p e r 4 l i n e s E t h = 2 k e V , L

• w

e r 4 l i n e s E t h = 4 k e V B G r a t e / k g / d a y 1 モジュ ー ルの質量 ( k g ) #

• f

m

• d

u l e s T

• l

a l m a s s ( k g ) E V E N T S / y e a r E R R O R / y e a r B G U p p e r l i m i t / y e a r ( 9 % C . L . ) U p p e r l i m i t ( / k g / d a y ) 1 . 7 2 E

• 2 0

. 4 5 8 8 1 6 . 7 3 4 4 . 5 1 E

• 1 0

. 6 7 1 5 5 6 1 . 4 1 7 5 0 . 5 2 8 7 3 1 . 7 2 E

• 2 0

. 4 5 8 8 2 5 6 1 . 1 7 4 4 7 . 2 2 E + 0 2 . 6 8 6 2 2 4 3 . 4 6 5 2 2 9 0 . 8 7 8 1 . 7 2 E

• 2 0

. 4 5 8 8 1 2 4 4 . 6 9 7 6 2 . 8 9 E + 1 5 . 3 7 2 4 4 8 6 . 9 3 4 5 8 0 . 4 3 9 1 . 7 2 E

• 2 0

. 4 5 8 8 2 1 7 6 9 . 9 8 2 4 6 . 1 3 E + 1 7 . 8 3 1 6 2 2 1 . 1 2 7 9 0 . 2 7 7 1 1 . 2 7 E

• 2 0

. 4 5 8 8 1 6 . 7 3 4 3 . 3 1 E

• 1 0

. 5 7 5 3 4 1 . 7 4 2 1 9 0 . 2 7 6 8 4 1 . 2 7 E

• 2 0

. 4 5 8 8 2 5 6 1 . 1 7 4 4 5 . 3 E + 0 2 . 3 1 3 6 3 2 . 9 6 8 7 5 8 0 . 6 9 2 1 1 . 2 7 E

• 2 0

. 4 5 8 8 1 2 4 4 . 6 9 7 6 2 . 1 2 E + 1 4 . 6 2 7 2 6 5 . 9 3 7 5 1 7 . 3 4 6 1 . 2 7 E

• 2 0

. 4 5 8 8 2 1 7 6 9 . 9 8 2 4 4 . 5 E + 1 6 . 7 9 5 6 9 8 . 6 5 5 3 4 4 0 . 2 3 7 4 N a I ( T l ) の厚さ . 1 c m B G 計数率 1 モジュ ー ルの質量 ( k g ) モジュ ール 数 全モジュ ー ルの質量 ( k g ) 1 年間の 計数値 1 年間の 計数誤差 B G 上限値 ( 9 % C . L . ) 計数値上 限値 ( / k g / d a y ) 2 . 7 4 E

• 2 0

. 9 1 7 5 1 6 . 1 4 6 8 1 . 4 4 E + 0 1 . 1 9 7 9 3 3 3 . 6 . 5 7 7 2 . 7 4 E

• 2 0

. 9 1 7 5 2 5 6 2 . 3 4 8 8 2 . 3 E + 1 4 . 7 9 1 7 3 2 2 . 9 1 E + 1 0 . 3 3 9 6 9 2 . 1 E

• 2 0

. 9 1 7 5 1 6 . 1 4 6 8 1 . 5 E + 0 1 . 2 4 9 6 4 2 . 4 5 7 0 . 4 5 8 2 4 2 . 1 E

• 2 0

. 9 1 7 5 2 5 6 2 . 3 4 8 8 1 . 6 8 E + 1 4 . 9 9 8 5 8 2 . 2 1 E + 1 0 . 2 5 7 5 8

Calculation of Exclusion plot

Upper limit on Rlim (Experimental result) Upper limit on Cross section σlim Local halo density ρ0=0.3GeV/cm3 Mean velocity <v>=230km/sec Target number density NT=4.013X1024/kg i f Coinc Th T EX

p p f R q F f v N m = =

lim 2 lim,

) ( ε ρ σ

χ

Exclusion plot for σEX

1 1 1 1

4

1 1

f u r

• s

h i k i 4

s _ l i m ( 1 6 m

• d

) s _ l i m ( 2 5 6 m

• d

) s _ l i m ( 1 2 4 m

• d

) s _ l i m ( 2 1 7 6 m

• d

) M A S S ( G e V )

Calculation of limit on σp-x

2 3 2 2 2 3 2 1 * 2

) 1 ( 1 2 1 2

∑ ∑

∆ +         + ∝ ∆ + +         + ∝

q q T T SD i f q q p M T T EX

q T J J m m m m p p q T M J J m m m m λ σ µ σ

χ χ χ χ

Using the relation, The Upper limit on proton-WIMPs cross section

EX T p T p p

J J m m m m m m J J

lim, * 2 2 2 2 lim,

1 2 1 2 ) 1 ( σ λ σ

χ χ χ

+ +         + + + =

−

Parameters

[ ]

GeV 18 . 118 GeV 938 . 2 7 , 2 5 75 . ) 1 (

I * 2

127 =

= = = = + m m J J J J

p p

λ

Expected sensitivity for WIMPs

Stringent limit will be obtained by 1year measurement

1

• 5

. 1 . 1 . 1 1 1

f u r

• s

h i k i 4

s x

• p

( 1 6 ) s x

• p

( 2 5 6 ) s x

• p

( 1 2 4 ) s x

• p

( 2 1 7 6 )

M A S S ( G e V )

SD Exclusion plot

Performance of thin NaI(Tl)

Thickness of NaI(Tl)

0.05cm

Energy resolution Energy threshold Photon number/keV Position selectivity PMT : Hamamatsu R329P

Development of thin NaI(Tl)

Collaboration with Horiba Ltd.

Production of thin NaI plate Selection of reflector

~2004/Feb.

Design and production method

2004/Apr.

First module was completed!!

2004/May~

Performance, stability test.

66mm 8mm 8mm

50mm 50mm

10mm 10mm

① ② ③ ④ ⑤ ⑥ ⑦ ⑧ ⑨

66mm

NaI(Tl)crystal(0.5mm)

Light Guide 1mm 1mm

アク リ ル 鉛シート

1mm 3mm

Production of thin NaI(Tl) by Horiba Ltd.

Test of performance

Thin NaI(Tl) scintillator Collimator

PMT① PMT④ PMT② PMT③

133Ba 57Co

Result (Preliminary)

30keV R(FWHM)=0.25 81keV R(FWHM)=0.13 122keV R(FWHM)=0.14

241Am

0.14 122keV

57Co

0.13 81keV

133Ba

0.18 60keV

241Am

0.25 30keV

133Ba

FWHM Energy Source

60keV R(FWHM)=0.18

⑦ ④ ① ⑧ ⑨

NaI(Tl) Real Position

⑤ ② ⑥ ③

Future Prospect

2005~2006

Underground experiment with 16 modules Laboratory: Oto Cosmo Observatory

Oto Cosmo Observatory

ELEGANT Group

RCNP/Osaka/Tokushima

Oto Cosmo Observatory 1400 m w.e

BG’s in OTO

Cosmic µ 4x10-3 /m2/s Neutron 4x10-1/m2/s 10 Bq/m3 Rn

Lab.II Lab.I, III

Nishiyoshino Oto

Entrance

Lab.I. 33 m2 ELEGANT VI ββ of 48Ca and DM with CaF2

• Lab. II. 45 m2

MOON-I, ββ of

100Mo and

DM with NaI 60 km south of Osaka, 150km east of Tokushima

The laboratory

Plan

Preparation of multi layer NaI(Tl)

~This Summer

Installation into OTO Cosmo Obs.

~This winter

Times π or 4π

Summary(1)

Signal Selection by

Spatial and Timing Correlation

Reduces the background events High sensitivity with a moderately pure detectors

Position resolution

Segmentation is most efficient way

Summary(2)

Development of thin NaI(Tl) array 5cmx5cmx0.05cm NaI(Tl) Successfully developed Purity of radioactivity

12µBq/kg for U 10mBq/kg for 210Pb

Good perfomance

18% FWHM at 60keV Eth~2-3keV