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

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

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, H 2 O, Ga experiments all showed significantly less flux than the SSM prediction. Neutrino oscillation naturally explained the results, but several solutions existed in (  m 2 - 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 (  m 2 ~10 5 eV 2 ) 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 ! [SNP]

6. Reactor: powerful tool for studying neutrino oscillation Pure and high intensity neutrino "beam" is provided. n+ 235 U→X+Y+2n Fission products: neutron rich →  - decays→[~6  's]+[~200MeV]/fission Typical power reactor (3GW th )→ 5.6×10 20 /s, ~1/4 is detected by e e The energy is low: The energy is low: E 8.5MeV→ < ~ The flux and the spectrum of are well understood. e [Power reactors] Isotopic components of the fuel elements ( 235 U, 239 Pu, 238 U, 241 Pu) 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% ! A large L/E factor in sin 2 is obtained  m 2 L 4E to be sensitive to small  m 2. e p→e + n Long history since the first detection of neutrinos by F.Reines in 1950's.

7. Reactor experiments e e e Detector Disappearance experiment 1-sin 2 2  sin 2  m 2 L 4E No oscillation up to a distance L~ O(1)km (  m 2 <O(10 -3 ) eV 2 ). e e p→e + n Neutrino flux has been well understood. The technique using a large volume (~10tons) liquid scintillator has been established. Before KamLAND, Liquid scintillator Cross section of has been understood very precisely (0.2%). e p→e + n N obs. /N no-oscil Reactor (L: flight distance)

8. KamLAND reactor neutrino experiments Kamioka 53 Japanese power reactors. 26 are concentrated at L=138-214km with 80GWth! <L>~180km KamLAND 1000ton LS With ~100 times larger L/E than before KamLAND is sensitive to  m 2 ~10 -5 eV 2 and can test the solar LMA solution!

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

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

11. Time and space correlation, and Delayed  energy → Significant reduction of backgorunds detection in KamLAND e p e+e+ ee n p d  (0.51)  (2.2MeV) [Prompt e + signal] [Delayed  by neutron capture] [E  1.8MeV] E prompt =T e+ + annihilation  ' s =E  0.8MeV ~200  s T e+ + pe + + n  e

12. Results of reactor Period Exposure (ton ・ y) |r p |,|r d |(m) |r p -r d | (m)  T p-d (  s) E d (MeV) E p (MeV) N no-osc.exp N obs N bkg 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 1st2nd 0.611±0.085±0.0410.658±0.044±0.047 [99.95%CL][99.998%CL] Phys.Rev.Lett. 94, 081801 (2005) 2.6MeV Disappearance ! Spectral Distortion N no-osc.exp [N obs -N bkg ]

13. Oscillatory behavior Decay Decoherence Oscillation L 0 /E distribution (180km) Δ m2=m2= 7.9 +0.6 -0.5 ×10 -5 eV 2 tan 2 θ= 0.4 +0.10 -0.07 Solar+KamLAND Oscillationparameters are precisely Determined ! 10 -5 10 -4 m2m2 eV 2  m 2 (eV) 2 tan 2  0.1 1 10 tan 2  5 6 7 8 9 10 4 11 12 ×10 -5

14. Prospects of KamLAND reactor expereiment “4  system” 3% rate error 1% scale error 3kt-yr data taking Keep data taking ! Reduce systematic error by a new calibration system in place of the vertical-axis calibration. 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 Now ready ! Systematic error : 6.5%

15. KamALND: challenging Geoneutrinos

16. Large heatflow from the Earth ~60mW/m 2 44.2±1.0 TW (Pollack, '93), 31±1 TW (Hofmeister, '05) (~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] 238 U(8TW), 232 Th(8TW), 40 K(3TW) 19TW Measured points >20,000

17. Geoneutrinos as a probe of Radiogenic Heat 40 K.511.5232.5 1.8MeV3.27MeV 214 Bi 212 Bi KamLAND 238 U 234 Pa 228 Ac 208 Tl 232 Th 238 U→ 206 Pb: 6 +51.7MeV 232 Th→ 208 Pb: 4 +42.7MeV 40 K→ 40 Ca+e - + +1.31MeV e e e [89%] Direct information of radiogenic heat ! (Eder('66), Marx('69))

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) Fiducial vol (|r p |, |r d |) < 5m |r p -r d | < 1m  T p-d 0.5  s- 500  s E prompt 0.9-2.6MeV EdEd Efficiency (68.7±0.7)% <5.5m < 2m 0.5  s- 1000  s same 2.6-8.5MeV (89.8±1.5)% [2nd reactor] [Geo  1.8-2.6MeV

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

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

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

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

23. KamLAND 7 Be Solar Neutrino Detection

24. Towards 7 Be solar Towards 7 Be solar 5MeV 300KeV Long lived 210 Pb(T 1/2 =22.3y) and 85 Kr(T 1/2 =10.8y) in the LS must be removed by factors ~10 5 ! SuperK SNO KamLAND 7 Be : Second largest flux. Theoretical Uncertainty is large (10%). No direct measurement so far. 7 Be (862KeV) Detection by KamLAND  e - →  e - Single ionization event with E vis <665KeV.

25. Purification of the 1000 ton LS LS Purification by Distillation ( 210 Pb) & N 2 purge ( 85 Kr) LS Construction of the purification system is finished this month ! Test plant (Tohoku University) 7 Be  Next year ! Lead removal (no oscillation) (~3×10 -5 reduction) Purification Method Distillation tower Tanks N 2 -purge tower 1.5m 3 /hr KamLAND area

26. Reactor & Geo-  after purification No reactor case ±35% After purification The same data taking period with enlarged fiducial volume. ±54%(now) Total data ±28% <30TW(99%CL) Check the Earth model ! No ( ,n) & Reduced accidentals Fiducial volume is enlarged ! Geo Reactor ( ,n) accidental Fast neutrons 16 O* 14 C* 6.5m (R/6.5m) 3 Fid. Volume Prompt Energy (MeV) 5.5m5m Reactor neutrino

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

28. RRRR tttt Remove 11 C by 3-fold coincidence ~95% of 11 C production is accompanied by neutrons 12 C+X→ 11 C+n+Y+ … X= ,n,p, ,e,  1)Muon 2)Neutron (2.2MeV   after ~200  s) 3) 11 C decay(  =29.4m) 11 C-n  + signal 200cm  select  L<50cm, #n detected >0) KamLAND 11 C detection Take 3-fold coincidence: 1.41.61.82.01.21.0 Visible energy (MeV)

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

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

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

32. KamLAND: Summary 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 has established e oscillation. Under the CPT invariance the SNP has been solved and oscillation parameters have been determined. KamLAND enters the solar phase next year. High quality data of reactor and geo-neutrinos will also be obtained. New "4  calibration system" has been ready for significant reduction of systematic errors to get improved measurement of oscillation parameters.