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05.09.19suekane 05 Erice School1 KamLAND F.Suekane Research Center for Neutrino Science Tohoku University suekane@awa.tohoku.ac.jp Erice School 2005.9.19
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05.09.19suekane 05 Erice School2 KamLAND Collaboration
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05.09.19suekane 05 Erice School3 Contents * Introduction to KamLAND * Physics with e Reactor- e Geo- e Solar- e * Future prospects 7 Be Solar phase 4 calibration system New Reactor * Summary
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05.09.19suekane 05 Erice School4 e world Main purpose of KamLAND is to explore the e world with; world largest & low-background liquid-scintillator e detector.
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05.09.19suekane 05 Erice School5 KamLAND Detector Cosmicray veto Balloon S.S. tank PMT Liquid Scintillator buffer oil Electronics
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05.09.19suekane 05 Erice School6 Oil Purification system Rn free N 2 Gas Generator Corridor to detector Water Purification system Monitor Displays
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05.09.19suekane 05 Erice School7 Key Detector Elements * Liquid Scintillator: Dodencane(80%)+PC(20%)+PPO(1.5g/L) (1150m 3 ) Light output ~8,000photons/MeV att. >10m * Balloon: 13m diam. 135 m thick Nylon/EVOH multilayer film. Held by Kevlar mesh. * PMT: 1325 17" aperture fast PMT (Newly developed) + 554 20" aperture (Kamiokande PMT) 34% photo-coverage * Purification system: Water extraction + N 2 bubbling U =>3.5x10 -18 g/g
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05.09.19suekane 05 Erice School8 Event Display: Cosmic-Ray Event
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05.09.19suekane 05 Erice School9 Event Display: Low Energy Event
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05.09.19suekane 05 Erice School10 Single Background 208 Tl decay ~2.5/day 238 U/ 222 Rn: 3.5x10 -18 g/g = 20 Bq 232 Th: 5.2x10 -17 g/g =100 Bq 40 K: <2.7x10 -16 g/g =<0.04Bq Reactor analysis threshold e threshold (cf: sea water contains10 -9 g/g of U.)
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05.09.19suekane 05 Erice School11 e detection ( e p -> e + n); an ideal reaction, because Only e contributes (no background from other neutrino species) Low threshold Energy (1.8MeV) Large cross section (~100 e ) p is abundant in LS Cross section precisely known ( =0.2%) e energy can be measured (E =E visible +0.8MeV) Delayed Coincidence -> powerful background rejection
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05.09.19suekane 05 Erice School12 e p crossection and neutron lifetime
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05.09.19suekane 05 Erice School13 - KamLAND can see * Reactor Neutrino -> Neutrino Oscillation * Geo Neutrino -> Heat Generation of Earth * Solar e if 0.01% of e -> e - But difficult to see * e from past SN * Atmospheric e - If e is observed at E>9MeV, => Unknown e source
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05.09.19suekane 05 Erice School14 A brief history of KamLAND Detector Construction 1997~ Start Data Taking 01/2002 1st reactor paper (deficit) 12/2002 (PRL 90:021802,2003) Solar e search 10/2003 (PRL 92:071301,2004) 2nd reactor paper 06/2004 (PRL 94, 081801,2005) (spectrum distortion) Geo neutrino paper 07/2005 (Nature 436:499-503,2005)
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05.09.19suekane 05 Erice School15 Reactor Neutrino
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05.09.19suekane 05 Erice School16 Reactor Neutrino ~6 /fission & ~200MeV/fission Neutrino Spectra E ~ a few MeV
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05.09.19suekane 05 Erice School17 e p cross section
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05.09.19suekane 05 Erice School18 Distance to the reactors 68GWth
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05.09.19suekane 05 Erice School19 If Neutrino Oscillation Exists => Deficit of neutrino events => Distortion of energy spectrum Thanks to the very long baseline and low reactor neutrino energy, KamLAND is sensitive with very low m 2. LMA region is covered!!
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05.09.19suekane 05 Erice School20 Event Selection Delayed Coincidence: 0.5 < ΔT < 1000μsec ΔR < 200 cm 1.8 < E delayed < 2.6 MeV Fiducial Volume: R prompt < 550 cm R delayed < 550 cm Spallation Cuts: ΔT μ > 2 msec ΔT μ > 2 sec (showering muons) or ΔL > 300 cm (non-showering) Energy Window: 2.6 < E prompt < 8.5 MeV (Mar. 9, 2002 ~ Jan. 11, 2004)
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05.09.19suekane 05 Erice School21
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05.09.19suekane 05 Erice School22 Neutrino Event Spectrum Probability of No Deficit =0.002% Probability of No Distortion=0.4% 258events 17.8events 365.2events expected arXiv:hep-ex/0406035 v3 Background
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05.09.19suekane 05 Erice School23 206 Pb+ 210 Po 138.4 d Back grounds
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05.09.19suekane 05 Erice School24 Distortion Pattern Oscillation back
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05.09.19suekane 05 Erice School25 Reactor Power Variation Consistent with Estimated BG No Oscillation Case
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05.09.19suekane 05 Erice School26 Oscillation Parameters KamLAND OnlyKamLAND+Solar Solar LMA Solution KamLAND only: KL+Solar: (PRL 94, 081801,2005)
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05.09.19suekane 05 Erice School27 Impact of the KamLAND Result to the Future Neutrino Physics sin2 and m 2 12 turn out to be not so small. (@ oscillation maximum; ) people Leptonic CP violation l may be accessible in the Future Experiments. Because CP asymmetry A CP can be large: (Not for the case of SMA or LOW solution)
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05.09.19suekane 05 Erice School28 Geo Neutrinos Nature 436, 28 July 2005
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05.09.19suekane 05 Erice School29 e p threshold U series: Q heat =49.7MeV Th series: Q heat =40.4MeV e from U/Th/K decay
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05.09.19suekane 05 Erice School30 U/Th abundance in the earth Observations: Chondristic Metrites (~average earth composition) contains a few 10ppb of U and Th. => ~4x10 17 kg of U+Th => The heat generation is ~15TW(40% of total heat dissipation) Earth crust contains a few ppm of U and Th Most of U,Th is concentrated in continental crust. distribution is roughly known. Radiogenic Heat Source of Earth PhD N.R.Tolich PhD S.Enomoto
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05.09.19suekane 05 Erice School31 Why Geo-Neutrinos? Observation of Geo neutrino Abundance and Localization of U and Th Thermal Structure and History of the earth - Is the earth cooling or equilibrium state? - What is the future of the earth? - What is the residual heat of the earth formation? - What drives the geo magnetic field?
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05.09.19suekane 05 Erice School32 expected e energy spectrum and event selection Data sample: live time 749.1d Event selection: Fiducial volume: R<5m T: 0.5 s-500 s R<1m E : 1.7-3.4 MeV (E promt : 0.9-2.6MeV) E delayed : 1.8-2.6MeV
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05.09.19suekane 05 Erice School33 Reactor 13 C( ,n) 16 O 238 U 232 Th Accidental Expected total backgrounds Expected total Observed e candidates 152 events Expected total backgrounds 127±13 events 25 +19 -18 events U+Th geo- Candidates: Rate only 2nd reactor results Geo- BSE model: 19 events
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05.09.19suekane 05 Erice School34 Rate + Shape analysis C.L. contours for detected U and Th geo- s. N U +N Th (N U N Th )/(N U +N Th ) Th/U mass Ratio=3.9 N U +N Th Prediction from the BSE model (19 events) Best fit: 3 U and 18 Th Geo- 's. 2 90%CL 4.5 54.2 N U +N Th : Consistent with prediction of geophysical model. of geophysical model. Geo- detection @95%! Th/U Mass ratio=3.9 U+T < 60TW (99%CL) Constraint by direct method!
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05.09.19suekane 05 Erice School35 e with E>9MeV There is no known e source with flux high enough to be detected by KamLAND. If any e events are observed, it is unknown e source.
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05.09.19suekane 05 Erice School36 Solar e No reactor region Two possibilities ( has to be Majorana) (1) (2)
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05.09.19suekane 05 Erice School37 Event selection 0.28kt year E=8.3MeV~14.8MeV => 0 event (1.1 +/- 0.4 BKG) f<3.7x10 2 /cm 2 /s (90%CL) <2.8x10 -4 of 8 B e Reacotr
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05.09.19suekane 05 Erice School38 e with E>15MeV * Relic SN e * Atmospheric e However, too few to be detected by KamLAND =>If KamLAND observes any e, it is unknown e source........ Analysis in progress.....
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05.09.19suekane 05 Erice School39 Flux Suppression for LMA pp& 7 Be- ~60% suppression Y.Suzuki But is it really so? Future of KamLAND Solar 7 Be detection
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05.09.19suekane 05 Erice School40 Back grounds Total 210 Po 210 Bi 85 Kr 7 Be 11 C 14 C 4 m radius fiducial 1.2 m cylindrical cut Required Reductions: 210 Pb: 10 -4 ~10 -5 85 Kr: ~10 -6 e scattering has to be used. Decayed coincidence can not be used
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05.09.19suekane 05 Erice School41 LS Purification Distillation System Test Bench N 2 gas purge (N 2 /LS = 25) Rn: ~1/10 Kr: ~1/100 Fractional Distillation (164 ℃, 300 hPa) Pb: 3×10 -5 Rn: 1×10 -5 Kr: < 2×10 -6 Required performance is almost achieved in small system & Purification system construction is starting. residual Pb might be organic lead (disintegrate at ~ 200 ℃ )
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05.09.19suekane 05 Erice School42 4 calibration system vertical calibration + uniformity of events 3dimensional calibration Improve fiducial volume error Improve sin 2 2 12 accuracy Installation 2005 Fall to reduce this error
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05.09.19suekane 05 Erice School43 New Reactor Shika-II L=88km (~ Oscillation Maximum) P th =3.926GW (~15% contribution) Increase of # of events will be small due to oscillation => confirmation of the measurement http://www.rikuden.co.jp/outline2/index.html Now 20062005 test operation schedule
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05.09.19suekane 05 Erice School44 Summary Reactor Neutrino Seen and m 2 =7.9x10 -5, tan 2 =0.46 with KamLAND only. Geo-neutrino Seen and consistent with earth models. Solar e Not seen. -> transition probability <2.8x10 -4 Preparation for solar 7 Be neutrino detection in progress new 4 calibration system being installed. new reactor at ~oscillation maximum started to operation.
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