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 neutrino experiment • KASKA experiment • Current R&D status – Boring test – Prototype detector – Electronics • Summary 2005.09.17 US-Japan seminar@Hawaii 2
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 8 Institutes Technology ~30 people 2005.09.17 US-Japan seminar@Hawaii 3
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 － 2005.09.17 US-Japan seminar@Hawaii 4
Θ 13 Limit: mixing matrix components • Experimental upper limit by CHOOZ – sin 2 2 θ 13 < 0.15 @ Δ m 2 13 = 2.5 x 10 -3 eV 2 ・ Last unknown lepton sector is Θ 13 ・ Result of sin 2 2 θ 13 measurement will indicate the possibility of CPV phase( δ 1 ) measurement 2005.09.17 US-Japan seminar@Hawaii 5
Measurement of θ 13 by reactor ν e disappearance: survival probability (P ee ) P ee ≈ 1 − sin 2 2 θ 13 sin 2 ∆ m 31 2 L − cos 4 θ 13 sin 2 2 θ 12 sin 2 ∆ m 21 2 L 4 E ν 4 E ν O (10 -3 ) sin 2 2 θ 13 Measure this small deficit � This is pure θ 13 measurement ( Δ m 2 12 << Δ m 2 23 , Δｍ 2 13 ) Baseline~O(1km) � matter effect negligible Need 1% accuracy for the measument 2005.09.17 US-Japan seminar@Hawaii 6
Neutrino spectrum from reactor • ν s are produced by β -decay from the fission products • One nuclear fission produces 6 ν e in average • 1GW reactor emits ~6x10 20 ν e /sec • 2.5% accuracy of E ν spectrum by β ray from fission products data ・ Detection method Cross section ν e +p → e + +n (E e =E ν -1.8MeV) e + +e - → 2 γ ( 0.511MeV) E signal =E ν – 0.8MeV>1.0MeV E ν (MeV) 2005.09.17 US-Japan seminar@Hawaii 7
KASKA experiment http://www.jp.wikipedia.org � Kashiwazaki –Kariwa nuclear power station - Largest power in the world (24.3GW) - 7 reactors in two cluster (3+4) K a s h i w a z a k i - K a r i w a （ 日） C H O O Z （ 仏） The world’s most powerful D i a b l o C a n y o n （ 米） reactor complex B r a i d w o o d （ 米） D a y a B a y （ 中） P=24.3GW th A n g o r a （ ブラ ジル） K r a s n o y a r s k （ 露） 0 5 1 0 1 5 2 0 2 5 3 0 S i t e P o w e r ( G W t h ) 2005.09.17 US-Japan seminar@Hawaii 8
Geometry of KASKA experiment • Two near detectors: ~400m Reactor and Detector Locations 2300 (~50m depth) #5 1800 #6 NEAR-B Detector #7 • One far-detector:1.7km 1300 FAR Detector 800 (~150m depth) #4 #3 300 NEAR-A Detector #2 Reactor-#1 -200 -500 0 500 1000 1500 2000 Relative Position (m) Location of far-detector is optimized by full oscillation 2005.09.17 US-Japan seminar@Hawaii 9
Detection method of anti-neutrino � Absorption by proton via inverse β -decay ν e + p → n + e + e + + e - → 2 γ (Ε=Εν−0.8 MeV) n + Gd → Gd’ + γ s ( Σ E γ ~8MeV) Delayed gammas emit after ~30 μ sec � ν can detected using delayed coincidence Delayed coincidence can drastically reduce the background 2005.09.17 US-Japan seminar@Hawaii 10
Detector under the ground ・ Shaft hole is designed - To reduce cosmic ray backgrounds - Already measured by boring test current design Near : ~100Hz - Shaft hole has horizontal tunnel Far : ~10Hz 2005.09.17 US-Japan seminar@Hawaii 11
KASKA Detector • Cylindrical detector Cosmic ray ν detector Gd-LS (90-180cm) tracker =10ton ( ρ =0.8) γ -catcher LS (70cm) Buffer Oil(70cn) 10”PMT*300, (13”*150) +2”PMT*50 Water Acrylic vessel Stainless steel tank Fe shield(10cm t ) Fe tank(1cm t ) 2005.09.17 US-Japan seminar@Hawaii 12
Systematic errors efficiency related + ν flux + BKG 2005.09.17 US-Japan seminar@Hawaii 13
Sensitivity Expected event rate @ far detector : 50,000/3years 1,200,000events/3years @ near detector • σ stat ~ 0.5% (rate only) 2.8% for CHOOZ • σ sys <1% 2.7% for CHOOZ • σ sys: 0.5%, � Sin 2 2 θ 13 ~0.015 2005.09.17 US-Japan seminar@Hawaii 14
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) 2005.09.17 US-Japan seminar@Hawaii 15
Prototype Detector • Detection of Gd- γ – Efficiency of γ -cather 1.2m • Background estimation from cosmic-ray spallation • Reactor neutrino detection – At JOYO: experimental fast reactor LS • Am/Be neutrino like signal – Prompt E p+ γ (visible)~5.5MeV – Emit neutron: captured after 30us Gd+ LS Box • LS contents – Pseudocumene(13.5%)+Iosparaffin( 86.5%)+PPO,BisMSB Am/Be source – Gd: 0.1% 2005.09.17 US-Japan seminar@Hawaii 16
Am/Be source w/o and w/ Gd y r a n i m i l • Observation of γ e r P spectrum from w/ Gd 8MeV – No cut – Low S/N w/o Ｇ ｄ 5.5 MeV y r a n i • Possible S/N m i l e r P improvement γ from – Shield around the Gd : 8MeV detector – Larger volume of Gd w/ Ｇ ｄ 4.5 MeV 7.0 MeV 2005.09.17 US-Japan seminar@Hawaii 17
Cosmic background - spallation y r a n Ｓ ｐ ａ ｌ ｌ ａ ｔ ｉ ｏ ｎ i m Ｆ ｉ ｔ ｔ ｉ ｎ ｇｆ ｕ ｎ ｃ ｔ ｉ ｏ i l e r ｎ ： P ｅ ｘ ｐ ＋ｅ ｘ ｐ ＋ｅ • Spallation event ｘ ｐ μ 1 2 C X * D e c a y + → → Ｂ Ｇ γ – Single rate must be <1Hz • <10Hz @ Prototype detector size: 1/30 y r Cosmic ray rate: x300 a n i m w/ Ｇ ｄ i – Time from Cosmic trigger l e r P After cuts of near surface event – >100usec: low rate – Full detector: 200usec deadtime 2005.09.17 US-Japan seminar@Hawaii 18 Passing time from cosmic
Cosmic background – correlated • Correlated background 9 L i 8 B e e ( 1 3 M e V ) n , ( τ 0 . 2 6 s , B r 4 8 % ) → + + + = = – BG must be <1 event/day � 10 event/day@prototype – Li window: Prompt(6~10MeV) Delayed(7~10MeV) – Larger volume of G ｄ 3 ｅ ｖ ｅ ｎ ｔ ７ ｅ ｖ ｅ ｎ ｔ w/ Ｇ ｄ w/o Ｇ ｄ Delayed Delayed y r y a n r a i m n i i m l e i r l P e r P Prompt Prompt 2005.09.17 US-Japan seminar@Hawaii 19
BG study of cosmic ray and γ ray • Boring Study @ near-B site electronics • 2004.10~11 Lead Shield Plastic Scintillators Reactor and Detector Location 2300 #5 1800 #6 NEAR-B Detector #7 1300 FAR Detector 800 #4 #3 300 NEAR-A Detector #2 Reactor-#1 -200 Hygrometer -500 0 500 1000 1500 2000 2005.09.17 US-Japan seminar@Hawaii 20 Relative Position (m)
y r a n i m Results of BG i l e r P 50m depth K U • γ ray background Th – The γ spectrum is well produced by Geant4 with ~60 γ - ray enegies – γ background rate • PMT<4Hz, y r a • soil+concreate<1Hz n i m i l e • Cosmic rate r P – Consistent with the estimation 2005.09.17 US-Japan seminar@Hawaii 21
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 2005.09.17 US-Japan seminar@Hawaii 22
Summary • KASKA is the θ 13 experiment from reactor neutrinos. – Most powerful reactor: Kashiwazaki-kariwa – Sensitivity: θ 13 ~0.015 at σ sys <0.5% • Now we study many tests using R&D budgets – Boring test : γ BG, 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! 2005.09.17 US-Japan seminar@Hawaii 23
Backup Slides 2005.09.17 US-Japan seminar@Hawaii 24
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[ 60cm thickness ] Energy Scaling by 60Co 34% escape probability for 1.2~1.3MeV γ ray 2005.09.17 US-Japan seminar@Hawaii 33
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Am/Be source + Gd (Ep = 4.5-7 MeV) [ Delayed spectrum ] Prompt: 4.5MeV ~ 7MeV Gd γの spectrum の Prototype は特にシールド など tail が見えないので， は設けていないので， 外部から のγ線 BG が多い S/N 比を向上さ せたい 中心部のプロンプト イ ベント でタ グする必要がある。 2005.09.17 US-Japan seminar@Hawaii 35
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