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Latest news from the KamLAND experiment

10 January, 2012, Valparaiso, Chile 4 th International Workshop on High Energy Physics in the LHC Era. Latest news from the KamLAND experiment. Yuri Efremenko for the KamLAND & KamLAND-Zen Collaborations University of Tennessee & IPMU . KamLAND Collaborators.

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Latest news from the KamLAND experiment

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  1. 10 January, 2012, Valparaiso, Chile 4th International Workshop on High Energy Physics in the LHC Era Latest news from the KamLAND experiment Yuri Efremenko for the KamLAND & KamLAND-Zen Collaborations University of Tennessee & IPMU

  2. KamLAND Collaborators Slides for this talk are shamelessly stolen from various members of the KamLAND collaboration

  3. Content • KamLAND detector • Reactor antineutrinos • Geo antineutrinos • Solar antineutrinos • Solar neutrinos • KamLAND-Zen • Summary

  4. 13m 18m KamLANDKamioka Liquid scintillator Anti-Neutrino Detector 1000m Shield from cosmic ray background ~10-5than at ground level External Layer is Water Shield instrumented by 225 20” PMT PMTs 17”·1325 + 20” ·554 Buffer  3 kt of mineral oil is a shielding from external background Resolution: Target  1 kt ultra pure liquid scintillator Space ~12cm / √E(MeV) Energy ~6.4% / √E(MeV) 238U : 3.5×10-18g/g 232Th : 5.2×10-17g/g in LS

  5. Detection scheme Antineutrino Inverse beta decay Prompt signal Te++ 1.022 MeV from annihilation = Eν- 0.8MeV • Vertex correlation • Time correlation • Delayed signal 2.2 MeV e- e e+ p n Delayed signal • (2.2 MeV) p ~210μsec x Neutrino ν-e elastic scattering x e- single vertex need low background e-

  6. Antineutrino Detection (colour is time) Prompt Signal E = 3.20 MeV Dt = 111 ms DR = 34 cm Delayed Signal E = 2.22 MeV ~ 1 antineutrino interaction per day e + p  e+ + n n + p  d +(2.2 MeV)

  7. Neutrino physics at the KamLAND The Sun Reactors x e ~500 events / day (7Be) ~1 event /day (8B) ~1event / day Verification of solar model Precision measurements of neutrino oscillation e e ~1event / 20days ? Verification of the Earth model Double beta decay Unexpected

  8. Neutrino Oscillations Weak and Mass Eigenstates For electron antineutrino disappearance:

  9. KamLAND and World Reactors 180km Distance of reactors from KamLAND Neutrinos @ KamLAND Japanese reactors : 94~97% Korean reactors : 3~5% World reactors : ~0.5% 80% is 130 ~ 220km θ13 θ12 Δm231 Δm221 suekane@ERICE09

  10. Neutrinos from nuclear Power Plants • From electric companies • Initial Fuel Composition • History of burn-up, and refueling • Time variation of thermal power Fission rate calculation for 235U, 238U, 239Pu, 241Pu + Neutrino spectrum for each fission Neutrino spectrum for each reactor PRL 90, 021802 (2003) PRL 94, 081801(2005) PRL 100, 221803(2008) PRD 83, 052002(2011)

  11. Energy spectrum & L/E plot (Observed) / (no osci. expected) Exposure : 4126 ton-year Direct evidence for neutrino oscillations, two periods of regeneration have been seen. No osci. expected : 2879±118 Background : 326±26 Observed events : 2106

  12. 3 flavor oscillation analysis sin2θ13 : 0.032 KamLAND only 0.020 KamLAND+solar +0.037 -0.037 Δm221 : 7.50 ×10-5eV tan2θ12: 0.450 +0.19 -0.20 +0.016 -0.016 +0.037 -0.031 Other sin2θ13 : measurements in 2011 +0.019 -0.018 +0.051 -0.020 DoubleChooz 0.022 T2K  0.032 MINOS  0.020 +0.062 -0.024

  13. Geo Neutrinos They are coming from decays of isotopes with very long decay time Too short life time relative to the Earth ~5·109 years history 235U (1/2=0.71109) y 237Np (1/2=0.002109) y 87Rb (1/2=49.7109) y 138La (1/2=110.0109) y 176Lu (1/2=21.0109) y 238U (1/2=4.47109) y 232Th (1/2=14.0109) y 40K (1/2=1.28109) y Too low concentration to produce significant amount of heat Prime candidates as a source of the Earth heat

  14. Etr 238U  206Pb + 84He + 6e- + 6e + 51.7 [MeV] 232Th  208Pb + 64He + 4e- + 4e + 42.7 [MeV] 40K  40Ca + e- + e+ 1.31 [MeV] 40K + e-  40Ar + e + 1.505 [MeV] Neutrinos from Decay Chains KamLAND is sensitive to antineutrinos from U and Th decay chains only Cross section

  15. Earth Heat Balance Surface heat flow Radiogenic heat > 44TW 19 TW Bulk Silicate Earth (BSE) model U : 8 TW Th : 8 TW K : 4 TW chondrite meteorite “Geo neutrinos” can directly tests radiogenic heat generation • Mines ( 4 km max) <0.001 of Earth radius • Boreholes (20 km max) • Seismology • Rocks from up to 200 km delivered by volcanic activity • Meteorites (Chondrite)

  16. Effect of neutrino oscillations Earth Cross Cut Geo Neutrino Signal at the KamLAND Earth Reference Model (based on Bulk Silicate Earth)

  17. Effect of Local Geology Average Uranium 2.32 ppm ＜５００km ５０％ Average Thorium 8.3 ppm 50% of the total flux originates from a distance > 500 km !!! Effect of local geology < 10% uncertainty of total flux

  18. Event rate time variation: 0.9 MeV - 2.6 MeV before-purification After correlation Data Reactor + BG + geo Best fit Rate, events/day Reactor + BG Reactor + BG Reactor+BG+geo Expected reactor We see constant contribution above the estimated reactor neutrino + non-neutrino background at 0.9 < E < 2.6 MeV region

  19. Observed Energy Spectrum: 0.9 MeV - 2.6 MeV 4126 ton-yr data-set (2135 days) Rate analysis (0.9 < E < 2.6 MeV) 841 candidates excess 111 events +45 -43

  20. Rate + Shape + Time analysis U/Th mass ratio fixed to 3.9 model w/o neutrino osc. best-fit (U, Th) (65, 33) U/Th ratio fixed Earth model prediction EPSL 258, 147 (2007) Nature 436, 28 (2005) PRL 100, 221803 (2008) Nature geoscience 4, 647 (2011) Ngeo = 106 events +29 -28 +1.2 Fgeo = 4.3 × 106 /cm2/sec -1.1 This is conformation that radiogenic is responsible to up to ~50% of the total heat emitted by the Earth

  21. Other Antineutrino Sources! There areno trivial antineutrino sources in the energy range 10-25 MeV Phys.Rev.D75:023007 Defuse Supernova Flux, various models • There is opportunity to look for antineutrinos: • from the Sun • diffuse supernova • Dark Matter annihilation

  22. Antineutrinos from the Sun? νe E. Akhmedov and J Pulido, Phys. Lett B 553, 7 (2003) SFP osc. Vacuum oscillations BT~107G Sun Layers νe production as function of radius mn is neutrino magnetic moment BT is the solar Magnetic Field

  23. KamLAND data in the 10-30 MeV range 4.53 kiloton-year Expected DSNF This region is not BG free. There is irreducible contribution from atmospheric neutrino NC interactions !! This is 2.5 times better that Borexino limit arXiv:1105.3516 [astro-ph] accepted to The Astrophysical Journal.

  24. + + ® + + n + 2 p p H e 0 . 42 MeV e 8B solar neutrino “pep” 0.25% “pp” 99.75% 14% “hep” 2.4*10-5 86% “7Be” 99.89% 0.11% “8B” 0.11% SK,SNO Borexino New measurement by the KamLAND

  25. 8B solar neutrino measurement 1432.1days data (Before LS purification, ~ April, 2007) 5.5MeV analysis threshold Best fit rate : 1.49±0.14(stat.)±0.17(syst.) ev/kton-day ɸES: 2.77±0.26(stat.) ±0.32(syst.) ·106/cm2/s Consistent with other experiments Mean : ɸES : 2.33±0.05 ×106/cm2/s (Dominated by SK measurement) Physical Review C 84, 035804 (2011)

  26. KamLAND-Zen(KamLAND with Zero Neutrino double beta decay search) Q N  b-  b-  2b- Z

  27. u u e- d e- d W - W - W- W- Two neutrinos or zero neutrino two beta decay? e- d e- νe νe d u u e-+ e- Energy, keV

  28. 0ν2β decay • Is neutrino Majorana particle? • Lepton number violation • Neutrino mass hierarchy • Effective neutrino mass Results from Neutrino experiments set target parameters for 0νββ decay search 0ν2βt1/2>1021~1025years (depending on nuclei)

  29. Search for 0ν2β decay with KamLAND miniballoon Decane 82% PC 18% PPO 2.7g/l Xenon 2.5wt% (91% Enriched 136Xe) • Requirement of 0ν2β decay experiment - Large isotope mass (for long half-life) - Ultra low background - Good Energy Resolution • Merit of using Xe - isotopic enrichment and purification well established - it is soluble into LS up to 3 wt%, - easily extracted back from scintillator R.S.Raghavan PRL.72.1411(1994) KamLAND proposal by Prof. A. Suzuki • Reactor, geo-neutrino, and SN watch can continue in parallel

  30. Expected spectrum at KamLAND-Zen Expected sensitivity • 2 years : ~ 80meV • 5 years : ~ 60meV 3.0wt% Xe(390kg) : 90% enriched 136Xe <m>=150meV Baloon : 25μm 232Th, 238U : 10-12g/g, 10C : 95% tag

  31. KamLAND Deck Modifications Need system to safely deploy Mini balloon into KamLAND detector

  32. Construction of KamLAND-Zen

  33. 3.16m Mini-balloon production May ~ Aug., 2011 in class 1 super clean room 7m Film check by eye Corrugated nylon tube Film 25μm 1 layer nylon 238U : 2×10-12g/g 232Th : 3×10-12g/g 40K : 2×10-12g/g Strings Film : ultrasonic cleaning by ultra-pure-water Strait part Balloon made by welding Film belt by nylon 1.5m 1.4m Cone part Sphere part (24 gores) All materials : washed by detergent, ultrasonic cleaning by ethanol and ultra-pure-water

  34. Aug., 2011 mini-balloon installation mini-balloon and corrugated tube deployment Balloon went through the black cover Piping line and load cell setting

  35. Scintillator Mini Balloon is very thin so Xe loaded scintillator should have same the density as the KamLAND scintillator Xe loaded LS KamLAND LS PC 17.7% PC 20% Decane82.3% Dodecane80% PPO(~2.7g/l) PPO(1.36g/l) Xe3.0wt% =

  36. Xe-LS filling Aug.~Sep., 2011 - mini-balloon was inflated with LS (w/o Xe) - DAQ for leak check - Dummy-LS replaced with Xe-loaded LS (0.02% density difference For separation from LS) - 330kg Xeis in mini-balloon - DAQ for KamLAND-Zen started on 24 Sep, 2011 Check by monitor camera LS Xe-LS supply tube mini-balloon surface welding lines

  37. Summary • KamLAND have observed reactor neutrinos, geo-neutrinos, solar neutrinos, atmospheric neutrinos. • Detection of Geo neutrinos started a new brunch  Neutrino Geo Physics • Set new limits on Defuse Supernova flux, and probability of conversion neutrinos into antineutrinos in strong solar magnetic field p < 5.3·10-5 • For reactor neutrino 3 flavor oscillation analysis of Solar + KamLAND: tan2θ12 = 0.450 Δm221 =7.50 ·10-5eV sin2θ13 : 0.020 • 8B solar neutrino - ɸES : 2.77±0.26(stat.) ±0.32(syst.)×106/cm2/s • KamLAND-Zen started in Sep. 2011 • KamLAND continues with reactor, geo, and SN neutrinos program +0.016 -0.016 +0.19 -0.20 +0.037 -0.031

  38. KamLAND2-Zen Future upgrades 2014~ partially funded 10m =~180kPa 1000kg 136Xe Pressurized ~ 6wt% Winston cone photo-coverage ×2 photon collection ×1.8 LS renewal KamLAND LS 8,000 ×1.4 (standard LS 12,000) Total light yield ×2.5 Low 2νββ G.B. ~20meV/5year Chimney enlargement Capability to accommodate CaF2, CdWO4, NaI, PBq 144Ce, and others

  39. Purification methods Solubility of ions : water >> LS wash scintillator with water 238U : 3.5×10-18g/g 232Th : 5.2×10-17g/g

  40. 2nd purification methods • Methods: - Distillation for Bi (Pb), Tl, K - N2 purge for Kr, Ar • 1st purification April ~ August, 2007 • 2nd purification June, 2008 ~ Feb, 2009 238U : 0.2~2.2×10-18g/g 232Th : 1.9~4.8×10-17g/g

  41. L/E plot 3 flavor best fit ∆m221: 7.49 ×10-5 eV2 tan2θ12 : 0.436 sin2θ13 : 0.032 (Observed) / (no osci. expected) +0.20 -0.20 +0.102 -0.081 +0.037 -0.037 KamLAND only analysis Geo-neutrino : free parameter Confirmation for 2 cycles oscillation Direct evidence for neutrino oscillation

  42. 3 flavor oscillation analysis

  43. Oscillation parameters 2 flavor analysis 3 flavor analysis Δm221 : 7.50 ×10-5eV tan2θ12 : 0.446 +0.19 -0.20 Δm221 : 7.50 ×10-5eV tan2θ12 : 0.450 sin2θ13 : 0.020 +0.19 -0.20 +0.034 -0.031 +0.037 -0.031 +0.016 -0.016

  44. Japanese reactors (total 54 reactors) Working only 11 reactors Power output : ~ 20% for total Low reactor neutrino precise geo-neutrino measurement Geo-reactor search by constant component check

  45. Singles spectrum (B.G.) Requirements for reactor e detection 238U232Th~ 10-14 g/g 40K~ 10-15 g/g

  46. z y x Accidental Backgrounds Steel in the chimney region Contamination concentrated on balloon and in support ropes High rate of single gammas from natural background radiation (U, Th, K, …) can “accidentally” mimic prompt-delayed signal Varies greatly with energy and location within the detector. Reduced by time (T[0.5,1000]s) and spatial (R<2m, R<6m) cuts. • candidate events • background events removed by selection cuts

  47. Correlated Backgrounds: Cosmogenic Spallation Products • Muons interact with material producing: • fast neutrons - removed with 2ms veto after any detected muon • delayed neutron  emitters (9Li) - removed with 2 second veto around -track He8 thought to be a negligible contribution Cutting events correlated with muons removes almost all cosmogenic bg <10% deadtime introduced by all muon cuts

  48. Correlated Background: 13C(,n)16O Originating from Rn contamination, discovered after first publication low energy ~6 MeV 4.4 MeV Background Prompt E (MeV) S.Harissopulos et al., Phys Rev. C72, 062801

  49. Energy spectra for neutrinos • 235U + n → A + B + 6.1β + 6.1ν + 202 MeV + 2.4n • 238U + n(≥1MeV) → C + D + 5~7β + 5~7ν + 205 MeV + x n • 239Pu + n → E + F + 5.6β + 5.6ν + 210 MeV + 2.9n • 241Pu + n → G + H + 6.4β + 6.4ν + 212 MeV + 2.9n 235U : K. Schreckenbach et al. Phys. Lett. B 160 325 (1985) 239Pu, 241Pu : A. A. Hahn et al. Phys. Lett. B 218 365 (1989) 238U : P. Vogel et al. Phys. Rev. C 24 1543 (1981) Energy spectra of neutrinos were checked by Bugey experiment

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