1 / 32

KamLAND Results

KamLAND Results. Reactor. Earth. Junpei Shirai for the KamLAND Collaboration Tohoku University NOW2006, Conca Specchiulla, Italy Sep.10-15, 2006. SUN…. KamLAND. KamLAND ( Kam ioka L iquid scintillator A nit- N eutrino D etector). Expected neutrino spectra from various sources.

lucia
Télécharger la présentation

KamLAND Results

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. KamLAND Results Reactor Earth Junpei Shirai for the KamLAND Collaboration Tohoku University NOW2006, Conca Specchiulla, Italy Sep.10-15, 2006 SUN… KamLAND

  2. KamLAND(Kamioka Liquid scintillatorAnit- Neutrino Detector) Expected neutrino spectra from various sources K.Nakamaura et al Solar  Challenges real time detection of Low energy neutrinos ! Supernova  Geo  Reactor  Relic supernova  Properties of neutrinosand Neutrino-generation Mechanizms in nature. Atmospheric  Galactic  1: Reactor  experiment 2: Geo  detection 3: Solar  detection 1MeV 10MeV etc.

  3. KamLAND Collaboration A.Suzuki Tohoku University, Japan, California Institute of Technology, USA University Bordeaux 1, France, Drexel University, USA, IHEP, China, Kansas State University, USA, Triangle Universities Nuclear Lab., USA, University of Alabama, USA, University of Hawaii, USA, University of New Mexico, USA, University of Tennessee, USA, Lawrence Berkeley National Lab., USA, Louisiana State University, USA, Stanford University, USA ~90 physicists from 14 Institutes

  4. KamLAND Reacotor experiment

  5. Challenging the Solar Neutrino Problem (SNP) Long History since late 1960's! Cl, H2O, Ga experiments all showed significantly less flux than the SSM prediction. [SNP] Neutrino oscillation naturally explained the results, but several solutions existed in (m2-mixing angle) plane. SNO discovered active non-e component in the flux by using both CC (only e) and NC (total active ’s) reactions. This strongly suggests neutrino oscillation. The LMA (m2~105eV2) solution seems quite promising, but no single experiment uniquely determined the solution. A decisive experiment is needed using man-made neutrinos. Reactor experiments have played a crucial role in this point !

  6. e e < ~ e e p→e+n m2L 4E Reactor: powerful tool for studying neutrino oscillation Long history since the first detection of neutrinos by F.Reines in 1950's. Pure and high intensity neutrino "beam" is provided. n+235U→X+Y+2n Fission products: neutron rich → - decays→[~6's]+[~200MeV]/fission Typical power reactor (3GWth)→ 5.6×1020 /s, ~1/4 is detected by The energy is low: E8.5MeV→ A large L/E factor in sin2 is obtained to be sensitive to small m2. The flux and the spectrum of are well understood. [Power reactors] Isotopic components of the fuel elements (235U, 239Pu, 238U, 241Pu) are estimated by the initial ones and the thermal power. The flux and spectrum of each element is studied and the total flux uncertainty is ~2% !

  7. e e e Nobs./Nno-oscil e e p→e+n p→e+n m2L 4E Reactor experiments Disappearance experiment Reactor 1-sin22sin2 (L: flight distance) Detector Liquid scintillator Before KamLAND, No oscillation up to a distance L~ O(1)km (m2<O(10-3) eV2). e Neutrino flux has been well understood. Cross section of has been understood very precisely (0.2%). The technique using a large volume (~10tons) liquid scintillator has been established.

  8. 53 Japanese power reactors. 26 are concentrated at L=138-214km with 80GWth! KamLAND reactor neutrino experiments KamLAND 1000ton LS <L>~180km With ~100 times larger L/E than before KamLAND is sensitive to m2 ~10-5eV2 and can test the solar LMA solution! Kamioka

  9. KamLAND Detector Calibration device Site: Kamioka underground mine, Gifu prefect., 2700m.w.e. Cosmic muon rate: 0.34Hz Rn free air Rock Central Detector Stainless steel tank (18m) LS(Normal dodecane(80%)+Pseudo- cumene(20%) +PPO(1.5g/l)) Balloon(135mt; EVOH/3Ny/EVOH) Buffer oil (Normal dodecane+ iso-paraffin: 2.5mt, LS-BO=-0.04%) 13m 1325 17”PMTs+554 20”PMTs (34% of 4, 350p.e./MeV, t~1.9ns (17”PMT)) Outer Detector Pure water (3.2kton) 20m 225 20”PMTs

  10. Mt.Ikenoyama 1km KamLAND area Detector 2.2km Control room Rn-free gas system Water purification system Oil purification system To the mine entrance

  11. + p e+ + n  e detection in KamLAND [E1.8MeV] [Prompt e+ signal] (0.51) Eprompt =Te++ annihilation 's =E-0.8MeV e- e e+ Te+ p (0.51) n (2.2MeV) p [Delayed  by neutron capture] ~200s d Time and space correlation, and Delayed  energy → Significant reduction of backgorunds

  12. [Nobs-Nbkg] Nno-osc.exp Results of reactor  1st 2nd Phys.Rev.Lett. 94, 081801 (2005) Period Exposure (ton・y) |rp|,|rd|(m) |rp-rd| (m) Tp-d (s) Ed (MeV) Ep (MeV) Nno-osc.exp Nobs Nbkg Mar.4- Oct.6, '02 162 < 5m 1.6 m 0.5-660 1.8-2.6 > 2.6 86.8±5.6 54 1±1 Mar.9, '02- Jan.11,'04 766 5.5 2 0.5-1000 Same 2.6-8.5 365±23.7 258 17.8±7.3 2.6MeV Spectral Distortion 0.611± 0.085±0.041 0.658± 0.044±0.047 Disappearance ! [99.95%CL] [99.998%CL]

  13. Δ m2= +0.6 7.9 -0.5 +0.10 0.4 -0.07 L0/E distribution (180km) Oscillatory behavior Decoherence Decay Oscillation Solar+KamLAND Oscillation parameters are precisely Determined ! eV2 ×10-5 12 10-4 11 4 10 m2 m2 (eV)2 9 8 10-5 7 ×10-5eV2 6 5 tan2θ= 1 0.1 10 tan2 tan2

  14. Prospects of KamLAND reactor expereiment Keep data taking ! Reduce systematic error by a new calibration system in place of the vertical-axis calibration. Systematic error : 6.5% 3% rate error 1% scale error 3kt-yr data taking Detector (%) Fiducial vol. 4.7 Energy threshold 2.3 Efficiency of cuts 1.6 Live time 0.06 Reactor power 2.1 Fuel composition 1.0 e spectra 2.5 Cross section 0.2 “4 system” Now ready !

  15. KamALND: challenging Geoneutrinos

  16. Large heatflow from the Earth 44.2±1.0 TW (Pollack, '93), 31±1 TW (Hofmeister, '05) ~60mW/m2 Measured points >20,000 (~10,000 power reactors) The heat source has not been well understood. Volcanoes, earthquakes, Plate tectonics, Plume tectonics, Magnetic field of the Earth Dynamics of the Earth Radiogenic heat has been considered to be very important! Carbonacious chondrite : Chemical component of the earth [BSE (Bulk Silicate Earth) model] 238U(8TW), 232Th(8TW), 40K(3TW) 19TW

  17. e e e Geoneutrinos as a probe of Radiogenic Heat Direct information of radiogenic heat ! (Eder('66), Marx('69)) 238U→206Pb: 6 +51.7MeV 40K→ 40Ca+e-+ +1.31MeV [89%] 232Th→208Pb: 4 +42.7MeV KamLAND 208Tl 234Pa 40K 228Ac 238U 232Th 212Bi 214Bi .5 1 1.5 2 2.5 3 1.8MeV 3.27MeV

  18. KamLAND: Geo- Analysis Data sample: Live-time 749.1±0.5 days (Mar.'02-Nov.'04) Selection conditions (after the on cut) Low energy (<3.3MeV) Background (external , radio-impurity) [Geo  [2nd reactor] <5.5m Fiducial vol (|rp|, |rd|) < 5m < 2m |rp-rd| < 1m Tp-d0.5s- 500s 0.5s- 1000s 2.6-8.5MeV Eprompt0.9-2.6MeV same 1.8-2.6MeV Ed Efficiency (68.7±0.7)% (89.8±1.5)%

  19. Reactor ν Energy spectra in KamLAND Nature 436, 499 (2005) Geo-ν Reactor  Data Events/0.17MeV BG-total (α,n) (42±11) Accidentals (80.4±7.2) Th U,Th prediction of the Earth model (16TW) (2.38±0.01) U Antineutrino Energy E(MeV) Observed: 152 events Estimated BG: 127±13 events +19 25 events -18

  20. Rate+Shape analysis The Earth model (Th/U mass ratio =3.9) U+Th=19 U/Th free Th/U mass ratio=3.9 NU+NTh(eventa) 90%CL 2 54.2 4.5 (NUNTh)/(NU+NTh) U+Th=21 (U=3, Th=18) NU+NTh (events) U+Th=28 Consistent with the rate analysis (25 ) and the Earth model (19) within 1σ. +19 -18 Radiogenic Power < 60TW (99%CL)

  21. (,n) Background 222Rn Geo Reactor 210Pb 210Bi 210Po (t1/2=22.3y) n+p→n+p 5.3MeV) Quenched, 21.1Bq/FV 206Pb 13C→16O(*)+n [1%] 16O* 12C* Primary 16O*→, e+e- (~6MeV) n+p→n+p n+12C→12C*(4.4)+n Uncetainty: 26% 4% (New data) Cross section 20% 210Po rate 14% Proton quench 10% Events <0.9MeV Measurement with n beam Secondary n+p→d+

  22. Reduce uncertaity of (,n) Measurement of the proton quenching factor in n+p→n+p. Hit the LS with mono-energetic neutrons to measure visible energy of the recoil proton in n+p→n+p. Neutron detectors (En, n) Preliminary LS sample OKTAVIAN @OSAKA Univ. Measure (,n) events in KamLAND below 0.9MeV; pure (,n) events to know 210Po decay rate. → Continued, Needs statistics. New cross section data of 13C(,n)16O. Harissopulous et al. (2005), sys. uncertaity 20%→4%.

  23. KamLAND 7Be Solar NeutrinoDetection

  24. KamLAND SuperK SNO Towards 7Be solar  7Be (862KeV) 7Be : Second largest flux. Theoretical Uncertainty is large (10%). No direct measurement so far. 300KeV 5MeV Detection by KamLAND e-→e- Single ionization event with Evis<665KeV. Long lived 210Pb(T1/2=22.3y) and 85Kr(T1/2=10.8y) in the LS must be removed by factors ~105!

  25. Purification of the 1000 ton LS Lead removal LS Purification Method Purification by Distillation (210Pb) & N2 purge (85Kr) Test plant (Tohoku University) LS 1.5m3/hr KamLAND area Next year ! Distillation tower (~3×10-5 reduction) Tanks N2-purge tower 7Be (no oscillation) Construction of the purification system is finished this month !

  26. Reactor  5m 5.5m 6.5m Reactor & Geo-after purification 16O* No (,n) & Reduced accidentals 14C* Fast neutrons Prompt Energy (MeV) Reactor neutrino Fiducial volume is enlarged ! accidental (,n) (R/6.5m)3 Fid. Volume Geo  No reactor case The same data taking period with enlarged fiducial volume. After purification ±54%(now) ±35% <30TW(99%CL) Total data ±28% Check the Earth model !

  27. 10-6 reduction of 210Pb, 85Kr assumed Towards pep/CNO  detection After removal of 210Pb and 85Kr, 11C which is generated by muons makes a dominant BG in 1~2 MeV region for pep/CNO  detection. 11C→11B+e++ =29.4m, Q=1.98MeV pep

  28. Dt DR Remove 11C by 3-fold coincidence ~95% of 11C production is accompanied by neutrons 12C+X→11C+n+Y+… X=,n,p,,e, Take 3-fold coincidence: Muon Neutron (2.2MeV after ~200s) 11C decay(=29.4m) + signal 1.0 1.2 1.4 1.6 1.8 2.0 Visible energy (MeV) KamLAND 11C detection 11C-n select L<50cm, #ndetected>0) 200cm

  29. 3 years data 7Be 11C CNO pep Pep/CNO : prospects Issues: New electronics to detect neutrons after the large muon signal (design finished). Next slide Improve muon fitter and muon tracking device. 5% of 11C remains.

  30. Electronics for 11C tagging Design finalized Main Circuit High multiplicity events after the muon (spallation neutrons) with absolutely zero dead-time and quick recovery Analogue Front End Circuit ×12 /main board

  31. 232Th: 212Bi→212Po KamLAND 0.17mBq/m3 Mar-Sep,2002 8B solar  To find upturn toward the low energy by the Matter effect. 232Th concentration in the LS is (5.2±0.8)×10-17 g/g from Bi→Po decay. 208Tl (→, 5MeV) in the LS dominates the signal. (64%) 212Bi 212Po (36%)   208Tl 208Pb from Pena-Garay If Th is removed by purification to ~10-3, then we have a chance !

  32. KamLAND: Summary KamLAND has established e oscillation. Under the CPT invariance the SNP has been solved and oscillation parameters have been determined. New "4 calibration system" has been ready for significant reduction of systematic errors to get improved measurement of oscillation parameters. First challenge of Geo-neutrino detection has been made by KamLAND. Further reduction of systematic uncertainty of (,n) background is underway. Construction of a new purification system is finished this month and we start LS purification right away. KamLAND enters the solar phase next year. High quality data of reactor and geo-neutrinos will also be obtained.

More Related