KASKA Experiment US-Japan seminar on Double beta decay and - - PowerPoint PPT Presentation

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KASKA Experiment US-Japan seminar on Double beta decay and - - PowerPoint PPT Presentation

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KASKA Experiment US-Japan seminar on Double beta decay and Neutrino mass on Sep.17 th ,2005@Hawaii K.Nitta, Tokyo Institute of Technology For KASKA Collaboration 2005.09.17 US-Japan seminar@Hawaii 1 Contents Introduction to reactor

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SLIDE 1

2005.09.17 US-Japan seminar@Hawaii 1

KASKA Experiment

US-Japan seminar on Double beta decay and Neutrino mass

  • n

Sep.17th ,2005@Hawaii K.Nitta, Tokyo Institute of Technology For KASKA Collaboration

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SLIDE 2

2005.09.17 US-Japan seminar@Hawaii 2

Contents

  • Introduction to reactor neutrino experiment
  • KASKA experiment
  • Current R&D status

– Boring test – Prototype detector – Electronics

  • Summary
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SLIDE 3

2005.09.17 US-Japan seminar@Hawaii 3

KASKA Collaboration

  • Niigata Univ.
  • Tohoku Univ.
  • Tokyo Institute of

Technology (TIT)

  • Miyagi Univ. of Education
  • KEK
  • Kobe Univ.
  • Tokyo Metropolitan Univ. (TMU)
  • Hiroshima Institute of

Technology

8 Institutes ~30 people

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2005.09.17 US-Japan seminar@Hawaii 4

Neutrino Matrix

  • Maki-Nakagawa-Sakata mixing matrix

– If neutrinos are massive particles, it is possible that the mass eigenstates and the weak eigenstates are not the same:

From Solar,KamLAND From SK(atm),K2K －

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SLIDE 5

2005.09.17 US-Japan seminar@Hawaii 5

Θ13 Limit: mixing matrix components

  • Experimental upper limit by CHOOZ

– sin22θ13 < 0.15 @ Δm2

13= 2.5 x 10-3eV2

・ Last unknown lepton sector is Θ13

・ Result of sin22θ13 measurement will indicate the possibility of CPV phase(δ1) measurement

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SLIDE 6

2005.09.17 US-Japan seminar@Hawaii 6

Measurement of θ13 by reactor

฀ νe disappearance: survival probability (Pee)

Pee ≈ 1− sin2 2θ13 sin2 ∆m31

2L

4E ν         − cos4 θ13 sin2 2θ12 sin2 ∆m21

2L

4E ν        

sin22θ13 O(10-3)

Measure this small deficit This is pure θ13 measurement (Δm2

12<<Δm2 23,Δｍ213 )

Baseline~O(1km) matter effect negligible

Need 1% accuracy for the measument

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SLIDE 7

2005.09.17 US-Japan seminar@Hawaii 7

Neutrino spectrum from reactor

  • νs are produced by β-decay from the fission products
  • One nuclear fission produces 6νe in average
  • 1GW reactor emits ~6x1020 νe /sec
  • 2.5% accuracy of

Eν spectrum by β ray from fission products data

Eν(MeV)

・ Detection method νe+p →e++n (Ee=Eν-1.8MeV) e++e- → 2γ (0.511MeV) Esignal=Eν – 0.8MeV>1.0MeV

Cross section

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2005.09.17 US-Japan seminar@Hawaii 8

5 1 1 5 2 2 5 3 K a s h i w a z a k i

  • K

a r i w a （ 日） C H O O Z （ 仏） D i a b l

  • C

a n y

  • n

（ 米） B r a i d w

  • d

（ 米） D a y a B a y （ 中） A n g

  • r

a （ ブラ ジル） K r a s n

  • y

a r s k （ 露）

S i t e P

  • w

e r ( G W t h )

The world’s most powerful reactor complex P=24.3GWth

Kashiwazaki –Kariwa nuclear power station

  • Largest power in the world

(24.3GW)

  • 7 reactors in two cluster

(3+4)

http://www.jp.wikipedia.org

KASKA experiment

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SLIDE 9

2005.09.17 US-Japan seminar@Hawaii 9

Geometry of KASKA experiment

  • Two near detectors: ~400m

(~50m depth)

  • One far-detector:1.7km

(~150m depth)

Reactor and Detector Locations

  • 200

300 800 1300 1800 2300

  • 500

500 1000 1500 2000

Relative Position (m)

NEAR-A Detector NEAR-B Detector Reactor-#1 #2 #3 #4 #5 #6 #7 FAR Detector

Location of far-detector is optimized by full

  • scillation
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2005.09.17 US-Japan seminar@Hawaii 10

Detection method of anti-neutrino

Absorption by proton via inverse β-decay

νe + p → n + e+ e+ + e- → 2γ (Ε=Εν−0.8MeV) n + Gd → Gd’ + γs (ΣEγ~8MeV)

Delayed gammas emit after ~30μsec νcan detected using delayed coincidence Delayed coincidence can drastically reduce the background

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2005.09.17 US-Japan seminar@Hawaii 11

Detector under the ground

・ Shaft hole is designed

  • To reduce cosmic ray backgrounds
  • Already measured by boring test
  • Shaft hole has horizontal tunnel

current design Near : ~100Hz Far : ~10Hz

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2005.09.17 US-Japan seminar@Hawaii 12

KASKA Detector

  • Cylindrical detector

γ-catcher LS (70cm) Buffer Oil(70cn) Water 10”PMT*300, (13”*150) +2”PMT*50 Cosmic ray tracker

Acrylic vessel Stainless steel tank Fe tank(1cmt) Fe shield(10cmt) ν detector Gd-LS (90-180cm)

=10ton (ρ=0.8)

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2005.09.17 US-Japan seminar@Hawaii 13

Systematic errors

efficiency related + ν flux + BKG

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2005.09.17 US-Japan seminar@Hawaii 14

Sensitivity

  • σstat ~ 0.5%

2.8% for CHOOZ

  • σsys<1%

2.7% for CHOOZ

  • σsys: 0.5%,

Sin22θ13~0.015 Expected event rate @ far detector : 50,000/3years

1,200,000events/3years @ near detector

(rate only)

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SLIDE 15

2005.09.17 US-Japan seminar@Hawaii 15

Present status of KASKA R&D

  • R&D budgets have been

approved in JFY2004~2005

  • Prototype detector
  • Boring study at near-B site
  • Electronics development
  • LS developments (another budget 2005-2006)
  • Detector and Shaft hole design study
  • Cosmic-ray detector development (2005-2006)
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2005.09.17 US-Japan seminar@Hawaii 16

Prototype Detector

  • Detection of Gd-γ

– Efficiency of γ-cather

  • Background estimation from

cosmic-ray spallation

  • Reactor neutrino detection

– At JOYO: experimental fast reactor

  • Am/Be neutrino like signal

– Prompt Ep+γ(visible)~5.5MeV – Emit neutron: captured after 30us

  • LS contents

– Pseudocumene(13.5%)+Iosparaffin( 86.5%)+PPO,BisMSB – Gd: 0.1% 1.2m

LS

Am/Be source Gd+ LS Box

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SLIDE 17

2005.09.17 US-Japan seminar@Hawaii 17

Am/Be source w/o and w/ Gd

8MeV 5.5 MeV γ from Gd : 8MeV 4.5 MeV 7.0 MeV

P r e l i m i n a P r e l i m i n a r y

w/o Ｇ ｄ w/ Ｇ ｄ

r y

  • Observation of γ

spectrum from w/ Gd

– No cut – Low S/N

  • Possible S/N

improvement

– Shield around the detector – Larger volume of Gd

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SLIDE 18

2005.09.17 US-Japan seminar@Hawaii 18

Cosmic background - spallation

Ｓ ｐ ａ ｌ ｌ ａ ｔ ｉ ｏ ｎ

Ｆ ｉ ｔ ｔ ｉ ｎ ｇｆ ｕ ｎ ｃ ｔ ｉ ｏ

m i n a r y

  • Spallation event

– Single rate must be <1Hz

  • <10Hz @ Prototype

detector size: 1/30 Cosmic ray rate: x300

– Time from Cosmic trigger – >100usec: low rate – Full detector: 200usec deadtime D e c a y X C μ

* 1 2

→ → +

P r e l i m i n a r y

Passing time from cosmic

w/ Ｇ ｄ

After cuts of near surface event

Ｂ Ｇ γ

ｎ ： ｅ ｘ ｐ ＋ｅ ｘ ｐ ＋ｅ ｘ ｐ

P r e l i

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SLIDE 19

2005.09.17 US-Japan seminar@Hawaii 19

Cosmic background – correlated

  • Correlated background

– BG must be <1 event/day 10 event/day@prototype – Li window: Prompt(6~10MeV) Delayed(7~10MeV) – Larger volume of Gｄ

4 8 % ) B r . 2 6 s , ( τ n , ( 1 3 M e V ) e B e L i 8

9

= = + + →

+

Prompt Delayed

７ ｅ ｖ ｅ ｎ ｔ 3 ｅ ｖ ｅ ｎ ｔ

Prompt Delayed

w/oＧ ｄ w/ Ｇ ｄ

P r e l i m i n a r y P r e l i m i n a r y

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SLIDE 20

2005.09.17 US-Japan seminar@Hawaii 20

BG study of cosmic ray and γray

  • Boring Study

@ near-B site

  • 2004.10~11

Plastic Scintillators

Lead Shield Hygrometer electronics

Reactor and Detector Location

  • 200

300 800 1300 1800 2300

  • 500

500 1000 1500 2000

Relative Position (m)

NEAR-A Detector NEAR-B Detector Reactor-#1 #2 #3 #4 #5 #6 #7 FAR Detector

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SLIDE 21

2005.09.17 US-Japan seminar@Hawaii 21

  • γ ray background

– The γ spectrum is well produced by Geant4 with ~60 γ- ray enegies – γ background rate

  • PMT<4Hz,
  • soil+concreate<1Hz
  • Cosmic rate

– Consistent with the estimation

50m depth

P r e l i m i n a r y

K U Th

P r e l i m i n a r y

Results of BG

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2005.09.17 US-Japan seminar@Hawaii 22

Electronics & DAQ

  • CAMAC based DAQ

prototype

  • VME bus or Compact

PCI bus system for the full spec detector

  • Now we develop new

1GHz FADC board

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SLIDE 23

2005.09.17 US-Japan seminar@Hawaii 23

Summary

  • KASKA is the θ13 experiment from reactor

neutrinos.

– Most powerful reactor: Kashiwazaki-kariwa – Sensitivity: θ13 ~0.015 at σsys<0.5%

  • Now we study many tests using R&D budgets

– Boring test : γBG, cosmic rate and neutron BG – Make and test: Prototype detector, Cosmic-ray tracker, Liquid scintillator, FADC and others

  • We now apply for full budget

– Construction from 2006 and data taking from end of 2008 if we can get!

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2005.09.17 US-Japan seminar@Hawaii 24

Backup Slides

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2005.09.17 US-Japan seminar@Hawaii 25

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2005.09.17 US-Japan seminar@Hawaii 26

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2005.09.17 US-Japan seminar@Hawaii 28

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2005.09.17 US-Japan seminar@Hawaii 29

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2005.09.17 US-Japan seminar@Hawaii 30

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2005.09.17 US-Japan seminar@Hawaii 31

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2005.09.17 US-Japan seminar@Hawaii 32

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2005.09.17 US-Japan seminar@Hawaii 33

Energy Scaling by 60Co

[ 60cm thickness ] 34% escape probability for 1.2~1.3MeV γ ray

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2005.09.17 US-Japan seminar@Hawaii 34

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2005.09.17 US-Japan seminar@Hawaii 35

Am/Be source + Gd (Ep = 4.5-7 MeV)

Gd γの spectrum の tail が見えないので， S/N 比を向上さ せたい [ Delayed spectrum ] Prompt: 4.5MeV ~ 7MeV

Prototype は特にシールド など は設けていないので， 外部から のγ線BGが多い 中心部のプロンプト イ ベント でタ グする必要がある。