International Workshop : Neutrino Research and Thermal Evolution of the Earth. KamLAND. Hiroko Watanabe

Transcription

1 International Workshop : Neutrino Research and Thermal Evolution of the Earth KamLAND Hiroko Watanabe Research Center for Neutrino Science (Tohoku Univ.) for the KamLAND Collaboration Tohoku University, Sendai, October 5-7, 16

2 Contents 1. KamLAND. Geo-neutrino Measurements 3. Analysis Results 4. Summary

3 Contents 1. KamLAND. Geo-neutrino Measurements 3. Analysis Results 4. Summary

4 KamLAND Collaboration 1/ K. Asakura 1, A. Gando 1, Y. Gando 1, T. Hachiya 1, S. Hayashida 1, H. Ikeda 1, K. Inoue 1,, K. Ishidoshiro 1, T. Ishikawa 1, S. Ishio 1, M. Koga 1,, S. Matsuda 1, T. Mitsui 1, D. Motoki 1, K. Nakamura 1,, S. Obara 1, T. Oura 1, I. Shimizu 1, Y. Shirahata 1, J. Shirai 1, A. Suzuki 1, H. Tachibana 1, K. Tamae 1, K. Ueshima 1, H. Watanabe 1, B. D. Xu 1,18, A. Kozlov, Y. Takemoto, S. Yoshida 3, K. Fushimi 4, A. Piepke,5, T. I. Banks 6,7, B. E. Berger,7, B. K. Fujikawa,7,T.O Donnell 6,7, J. G. Learned 8, J. Maricic 8, S. Matsuno 8, M. Sakai 8, L. A. Winslow 9, Y. Efremenko,1,11, H. J. Karwowski 1,13, D. M. Markoff 1,14, W. Tornow,1,15, J. A. Detwiler 16, S. Enomoto,16, and M. P. Decowski,17 The KamLAND Collaboration 1 Research Center for Neutrino Science, Tohoku University, Sendai , Japan * Institutions : 4 from Japan 1 from US 1 from Europe * ~5 collaborators Sep.

5 KamLAND Site and Detector KamLAND / Kamioka Liquid Scintillator Anti-Neutrino Detector : reactor Wakasa 146~19km (operated since ) Shika 88km Kashiwazaki 159km 18km Hamaoka km Kamioka Mine neutrino cosmic ray 1m depth φ13m balloon 1,t Liquid Scintillator ( 38 U: g/g, 3 Th: g/g) φ18m stainless tank Water Cherenkov Outer Detector 1,879 Photomultiplier Tubes * Photo coverage 34%

6 KamLAND 3/ KamLAND ~ Detector Features large volume & low backgrounds Physics observed energy [MeV] electron scattering ν + e ν + e inverse beta-decay ν e + p e + + n 6.5m 1, t Liquid Scintillator solar neutrinos reactor neutrinos PRL 1, 183 (8) geo neutrinos PRD 83, 5 (11) supernova neutrinos, etc. PRC 84, 3584 (11) PRC 9, 5588 (15) Nature Vol. 436 (5) Nature Geoscience 4, (11) PRD 88, 331 (13) PRL 9, 7131 (4) Astrophys. J. 745, 193 (11) Astrophys. J. 818, 91 (16) Different neutrino physics in a wide energy range

7 KamLAND-Zen 4/ KamLAND-Zen 11~ Zero Neutrino double beta decay search Detector Features 136 Xe loaded LS was installed in KamLAND (344 kg 9% enriched 136 Xe installed so far) Physics 6.5m 1.54m Xe loaded LS in a mini-balloon neutrino-less double beta decay World best limit on neutrino effective mass m < (61 165) mev PRL 117, 853 (16) Continue to use LS volume outside of miniballoon to measure anti-neutrino signals

8 Anti-neutrino Studies ν e flux ( 16 cm s 1 ) γ(.511mev) e - νe P e+ prompt γ(.511mev) ΔT=µsec n thermal diffusion delayed n P d inverse-beta decay γ(.mev) Geoneutrinos : Neutrino Application KamLAND Mantle Borexino Kamioka Gran Sasso 6 4 Radiogenic heat production from 38 U and 3 Th (TW) - Direct measurement of radiogenic heat contribution Events/1keV Survival Probability Geo e Reactor e Simulation no-oscillation oscillation [MeV] Neutrino Property Study 3- best-fit oscillation Data - BG - Geo e L /E (km/mev) e E p 5/ - Signature of neutrino oscillation - Precise measurement of oscillation parameters

9 Contents 1. KamLAND. Geo-neutrino Measurements 3. Analysis Results 4. Summary

10 Geo-neutrinos Electron-antineutrino from natural radioactive decay β-decay Geo-neutrinos /cm /sec e anti-neutrino detector 38 U 6/ 38 U! 6 Pb e +6 e +51.7MeV 3 Th! 8 Pb e +4 e +4.7MeV 3 Th 4 K! 4 Ca + e + e MeV (89.8%) Th Th U Th Th Th Th Th Th Th U Th U Th Th Number of anti-neutrinos per MeV per parent U series 3 Th series 4 K 1 1 Energy threshold, 1.8 MeV Anti-neutrino energy, E ν (MeV) Only geo-neutrinos from U and Th are detectable

11 Geo-neutrino Flux at Kamioka 7/ Distance and Cumulative Flux Cumulative flux (1/cm /sec) sediment crust mantle total Distance from KamLAND (km) utrino oscillation km Contributions from each area - 5%: distance < 5km - 5%: distance < 5km - 1~%: from Kamioka mine ref) Enomoto et al. EPSL 58, 147 (7) Total Crust Mantle Sediment Percentage of total (%) Contributions from each part Crust : 7% Mantle : 7% Core : % Sediment etc. : 3% Important to understand Japanese geology ~5 km ~5km

12 Laser Proof Geo-neutrino Measurements with KamLAND KamLAND 5 Nature 398 geo-neutrino first measurement 8 July THE INTERNATIONAL WEEKLY JOURNAL OF SCIENCE NATUREJOBS Highlight India EARTHLY POWERS Geoneutrinos reveal Earth s inner secrets GLOBAL CLIMATE Vital CO flux from Amazon vegetation BREAST CANCER Gene signature for metastasis FORENSIC SCIENCE Everything has a fingerprint INSIDE: INDIAN LIFE SCIENCES 749 days proton-year geo-nu event ev (56% error) Events/. MeV Events/. MeV LS purification 11 N. Geo. 15 radiogenic heat direct measurement KamLAND data E p (MeV) 135 days proton-year geo-nu event 8 ev Data background best fit reactor ν e Reference geo ν e E p (MeV) (7% error) Best fit reactor ν e Accidental 13 C(α, n) 16 O Best fit geo ν e Best fit reactor ν e + background + best fit geo ν e low reactor phase ν e flux ( 16 cm s 1 ) KamLAND Mantle 14 KamLAND-Zen Borexino Kamioka Gran Sasso 6 4 radiogenic heat 1±9 TW Radiogenic heat production from 38 U and 3 Th (TW) 13 PRD 88, 331 (13) include low reactor phase data 991 days proton-year geo-nu event ev 8/ (4% error)

13 Contents 1. KamLAND. Geo-neutrino Measurements 3. Analysis Results 4. Summary

14 Current Data-set Reactor Neutrino /day) neutrino/cm 1 Neutrino flux ( March 11 earthquake Data provided according to the special agreements between Tohoku Univ. and Japanese nuclear power reactor operators. Total Wakasa-bay Kashiwazaki Shika Hamaoka Korea Others all Japanese reactor-off period 3/7 1/ PRD 88, 331 (13) 13 data-set : 991 days proton-year advantages { update 16 data-set : 391 days proton-year 9/ reactor neutrino low-reactor period geo-neutrino Reactor neutrino background is decreased significantly times of 13 data-set - low-reactor operation period : ~3.5 years livetime - all Japanese reactor-off period : ~. years livetime Precise understanding of reactor neutrino spectrum enhances geo-neutrino measurement.

15 Reactor Neutrino Spectrum 1/ (Daya Bay, arxiv: v1) (A) anti-neutrino spectrum - Reactor neutrino experiments reported that there was an excess of events in the region of 4-6 MeV. - Daya Bay, RENO, Double Chooz 6+8AD/6AD Data / Prediction cm / fission / MeV (B) 1.8 Daya Bay / prediction (Huber+Mueller) 1.4 (C) Antineutrino Energy (MeV) geo-neutrino energy region excess - Reactor neutrino spectrum for KamLAND analysis 13 paper : Huber + Mueller & Bugey-4 normalisation 16 preliminary : Daya Bay measurement result σ f (cm /fission) = (5.9±.1) 1-43 (uncertainty :.3%) Antineutrino Energy (MeV) - We confirmed that : 4-6 MeV excess has no impact on the geo-neutrino results. effect of reactor spectrum uncertainty is much smaller than the statistical uncertainty of geo-neutrino events. Fig. 9. Uncertainty components of generic spectrum. The inner plot shows the correlation matrix of the generic spectrum.

16 days Event Rate Time Variation (.9-.6 MeV) Result.5 MeV.6 Rate (events/day) (a).9-.6 before MeVLS purification Period : May 7 - Aug. 11 (after LS purification) Period 3: Oct Nov. 1 (after KamLAND-Zen 11/ start) after LS purification Year.6 < Ep < 8.5 MeV Period 1 Period Period Year after KamLAND-Zen start low reactor period Period 1 Period Period 3 LS purification LS purification KamLAND data Expected reactor ν e + backgrounds + geo ν e Expected reactor ν e + backgrounds Expected reactor ν e KamLAND-Zen construction Observed Rate (events/day).6.5 March 11.4 Earthquake.3..1 constant contribution of geo-neutrino Expected Rate (events/day) 3-4 Backgrounds 5 : LS purification non-neutrino Year backgrounds reduction Earthquake reactor neutrino reduction - Constant contribution of geo-neutrino Time information is useful to extract the geo-neutrino signal Ob Observed Rate (events/day) KamLAND-Zen start.5.4 reactor anti-neutrino + other backgrounds evolution of expected and observed rates at KamLAND for ν e s with energies betw a.5have MeV. The good points indicate agreement the measuredwith rates in aexpected coarse time binning, rate while the cur lack line), reactor ν e s + backgrounds (colored line), and reactor ν e s + backgrounds.3..1 long-term shutdown of Japanese reactor

17 Energy Spectrum (.9-.6 MeV) 1/ Efficiency (%) Events /.MeV model prediction : Enomoto et al. EPSL 58, 147 (7) 6 Data - BG - best-fit reactor νe KamLAND data Selection efficiency Best-fit reactor ν Accidental 18 e C(α, n) O Best-fit geo ν e Best-fit reactor ν e + best-fit geo ν e + BG (MeV) E p U contribution Th contribution Reference geo νe 16 Result Livetime : 39.9 days Candidate : 113 ev Background Summary 9 Li 3.4 ±.1 Accidental 114. ±.1 Fast neutron < C(α, n) 16 O 5.5 ±.6 Reactor ν e ± 33.8 Total ± 4.9

18 Energy Spectrum, Period 3 (.9-.6 MeV) Events/.MeV/day 13/ Livetime : days 16 Result Events /.1MeV KamLAND data Best-fit reactor ν e Accidental C(α, n) O Best-fit geo ν e Best-fit reactor ν e + BG + best-fit geo ν e E p (MeV) best-fit : Period 3 analysis model prediction : Enomoto et al. EPSL 58, 147 (7) Data - BG - best-fit reactor ν e Reference geo ν e PRD 88, 331 (13) Livetime : 351 days Ep(MeV) We measured clear distribution of geo-neutrino events.

19 Rate + Shape + Time Analysis (1) N Th ratio fixed NU vs NTh earth model prediction EPSL 58, 147 (7) [event] N U [TNU] 68.3% 95.4% 99.7% ratio fixed ratio fixed NU NTh χ χ model prediction : Enomoto et al. EPSL 58, 147 (7) 1 Flux [ 1 5 cm - s -1 ] best-fit model N U N Th signal rejection U / / / σ Th 3 +7/ / / σ 3σ σ 1σ 14/ 16 Result 3σ σ 1σ

20 Rate + Shape + Time Analysis () NU + NTh 5 + N Th N U ratio fixed (a) 68.3% 95.4% 99.7% (N - N Th ) / (N + N Th ) best-fit earth model prediction EPSL 58, 147 (7) U U (NU, NTh) = (13, 34) NU+NTh = 164 [event] χ 6 4 ratio fixed (b) 8σ 6σ 4σ σ N U + N Th model prediction : Enomoto et al. EPSL 58, 147 (7) [TNU] Flux [ 1 6 cm - s -1 ] best-fit model 15/ 16 Result signal rejection U+Th /-5 (17%) / / σ

21 Th/U Mass Ratio (1) 16/ - According to geochemical studies, 3 Th is more abundant than 38 U. Mass ratio (Th/U) in bulk silicate Earth is expected to be around 3.9. Models : : Allegre et al. (1986) 3.9 : McDonough & Sun (1995) 3.89 : Taylor (198) 3.85 : Anderson (7) 3.77 : Palm & O Neil (3) 3.76 : Hart & Zindler (1986) 3.71 : Lyubetskaya & Korenaga (7) 3.6 : Jagoutz et al (1979) 3.58 : Javoy et al. (1) - Chondrite samples analysis : Fall statistics for the meteorites identified and catalogued since 98 A.D. - Geo-neutrino observed rate can be converted to amount of Th & U assuming homogeneous distribution. Independent & direct measurement of entire Earth slide from McDonough, 15, in Ehime

22 Th/U Mass Ratio () χ 3 1 Th/U=3.9 chondrite data ( ) BSE models ( ) 9% 1σ Th/U mass ratio ref) chondrite data Best fit Th/U = Th/U < 17. (9% C.L.) Ordinary Chondrites : J. S. Goreva & D. S. Burnett, Meteoritics & Planetary Science 36, (1) Carbonaceous Chondrites : A. Rocholl & K. P. Jochum, EPSL 117, (1993) Enstatite Chondrites : M. Javoy & E. Kaminski, EPSL 47, 1-8 (14) ref) 13 paper Th/U < 19 (9% C.L.) We have a sensitivity of Th/U mass ratio of entire Earth. KamLAND best-fit is consistent with chondrite data and BSE models. 17/ 16 Result

23 Earth Model Comparison cm - s -1 ) 6 Flux ( 1 ν e 6 4 Geodynamical Geochemical Cosmochemical crust uncertainty 1 3 Radiogenic Heat from 16 Result KamLAND 68.3% C.L. 38 U + 3 Th (TW) cm - s -1 ) 6 Flux ( 1 e 6 4 PRD 88, 331 (13) Cosmochemical Geochemical Geodynamical KamLAND 68.3% C.L Radiogenic Heat from U + Th (TW) [BSE composition models] Geodynamical based on balancing mantle viscosity and heat dissipation 18/ Geochemical based on mantle samples compared with chondrites Cosmochemical based on isotope constraints and chondritic models

24 Future Prospect 19/ Uncertainty of Geo-neutrino Flux Measurement Simulation (assuming Earth model) reactor ON +.5 yr PRD 88, 331 (13) ~1% reactor OFF χ (b) 8σ Uncertainty of geo-neutrino flux measurement is decreased at the same level of our expectation. Measurement uncertainty gets close to uncertainty of Earth model prediction. It is important to improve accuracy of Earth model prediction, especially crust modelling. 6σ * best fit with ± 1σ /cm /s : ~18% 4σ σ N U + N Th * uncertainty of Earth model prediction : %

25 Summary / The KamLAND experiment measures anti-neutrino from various sources over a wide energy range. results are presented. - Low-reactor operation period : ~3.5 years (33% of total livetime), clear energy spectrum of geo-neutrino - geo-neutrino event measurement with 17% uncertainty ( ev). It is consistent with our expectation. - geoscience discussion - Th/U mass ratio : , consistent with chondrite data and BSE models - Observed flux : consistent with models, but started to disfavour cosmochemical model Measurement uncertainty gets close to the uncertainty of Earth model prediction. Next target : - Estimation of geo-neutrino contribution from mantle - Better understanding of crust model