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KamLAND

KamLAND. F.Suekane Research Center for Neutrino Science Tohoku University suekane@awa.tohoku.ac.jp. Erice School 2005.9.19. KamLAND Collaboration. * Introduction to KamLAND * Physics with n e Reactor- n e Geo- n e Solar- n e * Future prospects

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KamLAND

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  1. KamLAND F.Suekane Research Center for Neutrino Science Tohoku University suekane@awa.tohoku.ac.jp Erice School 2005.9.19 suekane 05 Erice School

  2. KamLAND Collaboration suekane 05 Erice School

  3. * Introduction to KamLAND * Physics with ne Reactor-ne Geo-ne Solar-ne * Future prospects 7Be Solar phase 4p calibration system New Reactor * Summary Contents suekane 05 Erice School

  4. Main purpose of KamLAND is to explore the ne world with; world largest & low-background liquid-scintillator ne detector. ne world suekane 05 Erice School

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

  6. Monitor Displays Water Purification system Rn free N2 Gas Generator Corridor to detector suekane 05 Erice School Oil Purification system

  7. Key Detector Elements * Liquid Scintillator: Dodencane(80%)+PC(20%)+PPO(1.5g/L) (1150m3) Light output ~8,000photons/MeV latt.>10m * Balloon: 13m diam. 135mm 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 + N2 bubbling U =>3.5x10-18g/g suekane 05 Erice School

  8. Event Display: Cosmic-Ray Event suekane 05 Erice School

  9. Event Display: Low Energy Event suekane 05 Erice School

  10. Single Background ne threshold Reactor n analysis threshold 238U/222Rn: 3.5x10-18g/g = 20mBq 232Th: 5.2x10-17g/g =100mBq 40K: <2.7x10-16g/g =<0.04Bq (cf: sea water contains10-9g/g of U.) 208Tl decay ~2.5/day suekane 05 Erice School

  11. ne detection • (nep -> e+n); an ideal reaction, because • Only ne contributes (no background from other neutrino species) • Low threshold Energy (1.8MeV) • Large cross section (~100sne) • p is abundant in LS • Cross section precisely known (ds=0.2%) • ne energy can be measured (En=Evisible+0.8MeV) • Delayed Coincidence -> powerful background rejection suekane 05 Erice School

  12. nep crossection and neutron lifetime suekane 05 Erice School

  13. - KamLAND can see * Reactor Neutrino -> Neutrino Oscillation * Geo Neutrino -> Heat Generation of Earth * Solar neif 0.01% of ne -> ne - But difficult to see * ne from past SN * Atmospheric ne - If ne is observed at E>9MeV, => Unknown ne source suekane 05 Erice School

  14. A brief history of KamLAND Detector Construction 1997~ Start Data Taking 01/2002 1st reactor paper (deficit) 12/2002 (PRL 90:021802,2003) Solar ne 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) suekane 05 Erice School

  15. Reactor Neutrino suekane 05 Erice School

  16. Reactor Neutrino Neutrino Spectra ~6n/fission & ~200MeV/fission En~ a few MeV suekane 05 Erice School

  17. nep cross section suekane 05 Erice School

  18. Distance to the reactors 68GWth suekane 05 Erice School

  19. 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 Dm2. LMA region is covered!! suekane 05 Erice School

  20. (Mar. 9, 2002 ~ Jan. 11, 2004) Event Selection Delayed Coincidence: 0.5 < ΔT < 1000μsec ΔR < 200 cm 1.8 < Edelayed < 2.6 MeV Fiducial Volume: Rprompt < 550 cm Rdelayed < 550 cm Spallation Cuts: ΔTμ > 2 msec ΔTμ > 2 sec (showering muons) or ΔL > 300 cm (non-showering) Energy Window: 2.6 < Eprompt < 8.5 MeV suekane 05 Erice School

  21. suekane 05 Erice School

  22. arXiv:hep-ex/0406035 v3 Neutrino Event Spectrum 365.2events expected 258events Probability of No Deficit =0.002% Probability of No Distortion=0.4% 17.8events Background suekane 05 Erice School

  23. 210Po 206Pb+a 138.4 d Back grounds suekane 05 Erice School

  24. Distortion Pattern Oscillation back suekane 05 Erice School

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

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

  27. <=n people Impact of the KamLAND Result to the Future Neutrino Physics sin2q12 and Dm212 turn out to be not so small. (@ oscillation maximum; ) Leptonic CP violationdl may be accessible in the Future Experiments. Because CP asymmetry ACP can be large: (Not for the case of SMA or LOW solution) suekane 05 Erice School

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

  29. ne fromU/Th/K decay U series: Qheat=49.7MeV Th series: Qheat=40.4MeV nep threshold suekane 05 Erice School

  30. U/Th abundance in the earth Radiogenic Heat Source of Earth PhD N.R.Tolich PhD S.Enomoto • Observations: • Chondristic Metrites (~average earth composition) contains • a few 10ppb of U and Th. • => ~4x1017kg 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. suekane 05 Erice School

  31. 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? suekane 05 Erice School

  32. expected ne energy spectrumand 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 (Epromt: 0.9-2.6MeV) Edelayed: 1.8-2.6MeV suekane 05 Erice School

  33. Geo- 2nd reactor results Expected total Expected total backgrounds Reactor  13C(,n)16O BSE model: 19 events 238U 232Th Accidental U+Th geo- Candidates: Rate only Observed e candidates 152 events Expected total backgrounds 127±13 events 25+19-18 events suekane 05 Erice School

  34. Rate + Shape analysis C.L. contours for detected U and Th geo-s. Th/U Mass ratio=3.9 Th/U mass Ratio=3.9 90%CL NU+NTh 2  4.5 54.2 (NUNTh)/(NU+NTh) NU+NTh Prediction from the BSE model (19 events) NU+NTh: Consistent with prediction of geophysical model. Geo- detection @95%! Best fit: 3 U and 18 Th Geo-'s. U+T < 60TW (99%CL) Constraint by direct method! suekane 05 Erice School

  35. ne with E>9MeV • There is no known ne source with flux high enough to be detected by KamLAND. • If any ne events are observed, it is unknown ne source. suekane 05 Erice School

  36. Solar ne Two possibilities (n has to be Majorana) (1) (2) No reactor region suekane 05 Erice School

  37. Event selection Reacotr n 0.28kt year E=8.3MeV~14.8MeV => 0 event (1.1 +/- 0.4 BKG) f<3.7x102/cm2/s (90%CL) <2.8x10-4 of 8B ne suekane 05 Erice School

  38. ne with E>15MeV * Relic SN ne * Atmospheric ne However, too few to be detected by KamLAND =>If KamLAND observes any ne, it is unknown ne source. ....... Analysis in progress..... suekane 05 Erice School

  39. Solar 7Be n detection Future of KamLAND Flux Suppression for LMA pp&7Be-n ~60% suppression But is it really so? Y.Suzuki suekane 05 Erice School

  40. Back grounds 4 m radius fiducial 1.2 m cylindrical cut 14C Total 85Kr 210Po 210Bi 7Be 11C Required Reductions:210Pb: 10-4~10-5 85Kr: ~10-6 ne scattering has to be used. Decayed coincidence can not be used suekane 05 Erice School

  41. LS Purification Distillation System Test Bench • N2 gas purge (N2/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 residual Pb might be organic lead (disintegrate at ~ 200℃) Required performance is almost achieved in small system & Purification system construction is starting. suekane 05 Erice School

  42. to reduce this error 4p calibration system • vertical calibration + uniformity of events • 3dimensional calibration • Improve fiducial volume error • Improve sin22q12 accuracy Installation 2005 Fall suekane 05 Erice School

  43. New Reactor Shika-II • L=88km (~ Oscillation Maximum) • Pth=3.926GW (~15% contribution) • Increase of # of events will be small due to oscillation => confirmation of the measurement Now test operation schedule 2005 2006 suekane 05 Erice School http://www.rikuden.co.jp/outline2/index.html

  44. Summary • Reactor Neutrino • Seen and Dm2=7.9x10-5, tan2q=0.46 with KamLAND only. • Geo-neutrino • Seen and consistent with earth models. • Solar ne • Not seen. n -> n transition probability <2.8x10-4 • Preparation for solar 7Be neutrino detection in progress • new 4p calibration system being installed. • new reactor at ~oscillation maximum started to operation. suekane 05 Erice School

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