1. 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

2. 05.09.19suekane 05 Erice School2 KamLAND Collaboration

3. 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

4. 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.

5. 05.09.19suekane 05 Erice School5 KamLAND Detector Cosmicray veto Balloon S.S. tank PMT Liquid Scintillator buffer oil Electronics

6. 05.09.19suekane 05 Erice School6 Oil Purification system Rn free N 2 Gas Generator Corridor to detector Water Purification system Monitor Displays

7. 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

8. 05.09.19suekane 05 Erice School8 Event Display: Cosmic-Ray Event

9. 05.09.19suekane 05 Erice School9 Event Display: Low Energy Event

10. 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.)

11. 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

12. 05.09.19suekane 05 Erice School12 e p crossection and neutron lifetime

13. 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

14. 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)

15. 05.09.19suekane 05 Erice School15 Reactor Neutrino

16. 05.09.19suekane 05 Erice School16 Reactor Neutrino ~6 /fission & ~200MeV/fission Neutrino Spectra E ~ a few MeV

17. 05.09.19suekane 05 Erice School17 e p cross section

18. 05.09.19suekane 05 Erice School18 Distance to the reactors 68GWth

19. 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!!

20. 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)

21. 05.09.19suekane 05 Erice School21

22. 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

23. 05.09.19suekane 05 Erice School23 206 Pb+  210 Po 138.4 d Back grounds

24. 05.09.19suekane 05 Erice School24 Distortion Pattern Oscillation back

25. 05.09.19suekane 05 Erice School25 Reactor Power Variation Consistent with Estimated BG No Oscillation Case

26. 05.09.19suekane 05 Erice School26 Oscillation Parameters KamLAND OnlyKamLAND+Solar Solar LMA Solution KamLAND only: KL+Solar: (PRL 94, 081801,2005)

27. 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)

28. 05.09.19suekane 05 Erice School28 Geo Neutrinos Nature 436, 28 July 2005

29. 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

30. 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

31. 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?

32. 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

33. 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

34. 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! 

35. 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.

36. 05.09.19suekane 05 Erice School36 Solar e No reactor region Two possibilities ( has to be Majorana) (1) (2)

37. 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

38. 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.....

39. 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

40. 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

41. 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 ℃ )

42. 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

43. 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

44. 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.