KamLAND Results. Neutrino Oscillation Workshop Sep. 8, 2008 I. Shimizu (Tohoku Univ.)

Transcription

1 KamLAND Results Neutrino Oscillation Workshop Sep. 8, 008 I. Shimizu (Tohoku Univ.)

2 KamLAND Collaboration S. Abe,1 T. Ebihara,1 S. Enomoto,1 K. Furuno,1 Y. Gando,1 K. Ichimura,1 H. Ikeda,1 K. Inoue,1 Y. Kibe,1 Y. Kishimoto,1 M. Koga,1 A. Kozlov,1 Y. Minekawa,1 T. Mitsui,1 K. Nakajima,1, K. Nakajima,1 K. Nakamura,1 M. Nakamura,1 K. Owada,1 I. Shimizu,1 Y. Shimizu,1 J. Shirai,1 F. Suekane,1 A. Suzuki,1 Y. Takemoto,1 K. Tamae,1 A. Terashima,1 H. Watanabe,1 E. Yonezawa,1 S. Yoshida,1 J. Busenitz, T. Classen, C. Grant, G. Keefer, D.S. Leonard, D. McKee, A. Piepke, M.P. Decowski,3 J.A. Detwiler,3 S.J. Freedman,3 B.K. Fujikawa,3 F. Gray,3, E. Guardincerri,3 L. Hsu,3, R. Kadel,3 C. Lendvai,3 K.-B. Luk,3 H. Murayama,3 T. OʼDonnell,3 H.M. Steiner,3 L.A. Winslow,3 D.A. Dwyer,4 C. Jillings,4, Åò C. Mauger,4 R.D. McKeown,4 P. Vogel,4 C. Zhang,4 B.E. Berger,5 C.E. Lane,6 J. Maricic,6 T. Miletic,6 M. Batygov,7 J.G. Learned,7 S. Matsuno,7 S. Pakvasa,7 J. Foster,8 G.A. Horton-Smith,8 A. Tang,8 S. Dazeley,9, Å K.E. Downum, G. Gratta, K. Tolich, W. Bugg,11 Y. Efremenko,11 Y. Kamyshkov,11 O. Perevozchikov,11 H.J. Karwowski,1 D.M. Markoff,1 W. Tornow,1 K.M. Heeger,13 F. Piquemal,14 and J.-S. Ricol14 (The KamLAND Collaboration) 1Research Center for Neutrino Science, Tohoku University, Sendai , Japan Department of Physics and Astronomy, University of Alabama, Tuscaloosa, Alabama 35487, USA 3Physics Department, University of California, Berkeley and Lawrence Berkeley National Laboratory, Berkeley, California 9470, USA 4W. K. Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, California 9115, USA 5Department of Physics, Colorado State University, Fort Collins, Colorado 8053, USA 6Physics Department, Drexel University, Philadelphia, Pennsylvania 194, USA 7Department of Physics and Astronomy, University of Hawaii at Manoa, Honolulu, Hawaii 968, USA 8Department of Physics, Kansas State University, Manhattan, Kansas 66506, USA 9Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA Physics Department, Stanford University, Stanford, California 94305, USA 11Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA 1Triangle Universities Nuclear Laboratory, Durham, North Carolina 7708, USA and Physics Departments at Duke University, North Carolina Central University, and the University of North Carolina at Chapel Hill 13Department of Physics, University of Wisconsin, Madison, Wisconsin 53706, USA 14CEN Bordeaux-Gradignan, INP3-CNRS and University Bordeaux I, F Gradignan Cedex, France

3 Reactor Neutrino

4 KamLAND Kamioka Liquid Scintillator Anti-Neutrino Detector Inner tank 1,000 ton LS Outer water tank Kamioka ~ 180 km baseline 34% photo-coverage with and PMTs flavor neutrino oscillation most sensitive region P (ν e ν e ) = 1 sin θ sin ( 1.7 m [ev ]l[m] E[MeV] ) m = (1/1.7) (E[MeV]/L[m]) (π/) 3 5 ev reactor neutrino : sensitive to LMA solution

5 Physics Target in KamLAND observed energy (MeV) solar neutrino geo neutrino reactor neutrino supernova neutrino solar neutrino ν x e - ν x reactor neutrino geo neutrino γ e + ν e p prompt γ delayed e - mean capture time ~ 00 µsec on proton n γ neutrino detection by electron scattering anti-neutrino detection by inverse beta-decay

6 Reactor and Geo Neutrino Analysis previous result S / B ratio map (energy v.s. radius) separated analysis window for reactor and geo neutrinos m 5.5 m S/N reactor neutrino ( MeV, R 5.5 m) geo neutrino ( MeV, R 5.0 m) Prompt Energy (MeV) Analysis improvement (R/6.5m) (1) efficient accidental background rejection () combined analysis of reactor and geo neutrinos large accidental B.G. caused by external γ-rays

7 Anti-Neutrino Event Selection (a) accidental B.G. discrimination 0.5 < ΔT < 00 µs ΔR < m 1.8 MeV < E delayed <.6 MeV or 4.0 MeV < E delayed < 5.8 MeV 0.9 MeV < E prompt < 8.5 MeV R prompt, R delayed < 6.0 m L-selection from 6 parameters (b) µ spallation cut ΔTµ > s after showing µ ΔTµ > s or ΔL > 3 m after non-showering µ (ΔQ < 6 p.e.) prompt delayed

8 Likelihood Selection L-selection for accidental B.G. discrimination Accidentals PDF Signal PDF L-selector Maximize Figure of Merit for each Ep bin Efficiency (%) efficiency Detection efficiency efficiency decrease caused by larger accidental BG Efficiency Figure of Merit Figure of Merit E prompt (MeV) Figure of Merit Events / Bin Figure of Merit accidental anti-neutrino background (reactor, geo) < Eprompt <.3 MeV generated by MC simulation Likelihood Ratio Figure of Merit maximum Figure of Merit Lratio > Likelihood Ratio

9 Systematic Uncertainty full volume calibration lowered the fiducial volume error (4.7% in previous analysis) Detector related Fiducial volume 1.8% Reactor related νe spectra.4% Energy scale 1.5% Reactor power.1% L-selection eff. 0.6% Fuel composition 1.0% OD veto 0.% Long-lived nuclei 0.3% Cross section 0.% Time lag 0.01%.4% 3.4% Total systematic uncertainty : 4.1%

10 Full Volume Calibration source deployment z-axis event rate (arbitrary) Bias [cm] off-axis Bias [cm] 4pi calibration system for the off-axis source deployment bias < 3 cm corresponds to 1.8% volume uncertainty cross-checked by 1 B/ 1 N uniformity Co 60 Co bias < 3 cm R [cm] 68 Ge off-axis off-axis 68 Ge bias < 3 cm R [cm] z-axis z-axis

11 (α, n) Background Estimation 13 C(α, n) 16 O α natural abundance 1.1% Q =.MeV 13 C 1 C n 16 O prompt γ (4.4MeV) 1 C(n, nγ) 1 C prompt γ (6.1MeV) or e + e - (6.0MeV) recoil proton 16 p O delayed n γ (.MeV) d 6.130MeV MeV cross section [barn] low energy 13 C(α, n) 16 O (g.s.) n. 4.4MeV 13 C(α, n) 16 O (g.s.) n 1 C(n, nγ) 1 C γ + n 3. 6MeV 13 C(α, n) 16 O* (1st e.s MeV) e + e - 13 C(α, n) 16 O* (nd e.s MeV) γ + n cross section measurement 1-6 S. Harissopulos et al. JENDL neutron yield difference < 4% alpha energy [MeV] total cross section was determined precisely Cross section for each branch should be measured

12 Cross Section Measurement direct measurement of 13 C(α, n) 16 O reaction in KamLAND Po 13 C source calibration Po 13 C source ground state 1st excited state nd excitted state Po/ 13 C mixture Delrin (α, n) background estimation ± 18.0 events for ground state 18.7 ± 3.7 events for excited state Estimation uncertainty 11% for ground state 0% for excited state

13 Rate Analysis above.6 MeV Reactor rate analysis (.6 MeV threshold) No osci. expected Background Observed events Ratio = (obs. - B.G.) / No osci. χ / ndf =.8 / ± 0.00(stat) ± 0.06(syst) 8.5σ disappearance significance Fit constrained through B.G. expected Fit with a horizontal line χ / ndf = 1.0 / 4 (1.7% C.L.) events/day observed rate [events/day] period for KamLAND days expected in no oscillation case 90% C.L. updated 976 days total 1491 days expected rate in no oscillation [events/day]

14 Energy Spectrum above 0.9 MeV Events / 0.45 MeV Efficiency (%) exposure : 881 ton-year ( ton-year for KamLAND 004 ) geo neutrinos previous result (above.6 MeV) Efficiency KamLAND data no oscillation best-fit osci. accidental C(!,n) O best-fit Geo " e best-fit osci. + BG + best-fit Geo " e best-fit Geo + Reactor combined analysis No osci. expected Background (w/o geo neutrino) Observed events (tan θ, Δm ) = (0.56, ev ) E p (MeV) free parameter : geo neutrinos (U, Th) = (37.1, 30.) events goodness of fit using equal probability bins best-fit χ / ndf = 0.9 / 16 (18.4% C.L.) no osci. χ / ndf = 63.6 / 17 Scaled no oscillation spectrum is excluded at 5.1

15 L/E Plot previous result (above.6 MeV) Survival Probability Data - BG - Geo! e Expectation based on osci. parameters determined by KamLAND L 0 /E!e (km/mev) ~ 1 cycle of oscillation

16 L/E Plot this result (above 0.9 MeV) Survival Probability Data - BG - Geo! e Expectation based on osci. parameters determined by KamLAND L 0 /E!e (km/mev) ~ cycle of oscillation strong evidence of neutrino oscillation

17 Alternate Hypothesis V. D. Barger et al., Phys. Rev. Lett. 8, 640 (1999) E. Lisi et al, Phys. Rev. Lett. 85, 1166 (000) short baseline experiment Survival Probability 1.4 Data - BG - Geo! e Expectation based on osci. parameters 1. determined by KamLAND CHOOZ data hypothetical single reactor at 180 km oscillation decoherence Δχ = 45.1 decay Δχ = L 0 /E!e (km/mev) best model is neutrino oscillation

18 Alternate Wavelength short baseline experiment Survival Probability 1.4 Data - BG - Geo! e Expectation based on osci. parameters 1. determined by KamLAND CHOOZ data hypothetical single reactor at 180 km LMA I LMA II LMA L 0 /E!e (km/mev) LMA 0 and LMA II are disfavored at more than 4σ

19 6! 5! 4! 1! 3!! Oscillation Parameters $# ) (ev 1 $m small matter effect Solar KamLAND -1 1 KamLAND 95% C.L. 99% C.L % C.L. best fit Solar " 1 95% C.L. 99% C.L % C.L. best fit 4! 3!! 1! > 6σ > 4σ tan $# KamLAND only tan θ = 0.56 LMA II ) ev -4 ( " m LMA sin! Δm = ev (marginalized error) 3 neutino neutino KamLAND(Rate+Shape+Time) 3 neutrino effect = Float 95% C.L. 99% C.L % C.L. sin! 13 = 0 95% C.L. 99% C.L % C.L sin! 1 same result for Δm

20 Precise Measurement of Δm ) (ev KamLAND tan θ = KamLAND + Solar 95% C.L. 99% C.L % C.L. global best fit Δm = ev This result KamLAND + Solar tan θ = Δm = ev Δm : systematic uncertainty.0% dominated by linear energy scale uncertainty 8 8 ) "m tan ev! -5 ( 1 "m 7 6 KamLAND + Solar 95% C.L. 99% C.L % C.L. best fit tan m is measured at.8% precision by KamLAND! 1

21 χ Map Release chimap_3rdresult/chimap.html KamLAND-only best-fit parameters : (tan θ, Δm ) = (0.56, ev ) KamLAND + Solar best-fit parameters : (tan θ, Δm ) = (0.47, ev ) Please use the constraints on oscillation parameters

22 Geo Neutrino

23 Inner Structure of the Earth - Inner structure of the earth was investigated by the seismic wave measurement - Total heat flow from the earth 44TW or 31 TW radiogenic heat generation 19 TW (U ~ 8 TW, Th ~ 8 TW, K ~ 3 TW) others (primordial heat, latent heat) from IHFC Radiogenic heat contribution is important to understand the earth dynamics

24 Neutrino from the Earth U series Th series anti-neutrinos from beta-decay Geo neutrino directly tests radiogenic heat generation

25 Geo Neutrino Estimation 40 0 Data - BG - best-fit osci. Reference Geo " e [8] Events / 0. MeV 0 10 KamLAND data best-fit osci. 0 accidental Reference model (16 TW) U : 56.6 event (9. TNU) Th : 13.1 event (7.7 TNU) total : 36.9 TNU E p (MeV) E p O C(!,n) best-fit Geo " e best-fit osci. + BG + best-fit Geo " e U+Th = TNU (previous result : TNU (Terrestrial Neutrino Unit) = events/ 3 target-proton/year event TNU)

26 Geo Reactor Constraint Natural nuclear fission reactor at the Earth s center small contribution to total heat flow? energy source of geo-magnetic field? KamLAND + Solar KamLAND only Events / 0.45 MeV Efficiency (%) geo reactor ( TW) Efficiency KamLAND data no oscillation best-fit osci. accidental C(!,n) O best-fit Geo " e best-fit osci. + BG + best-fit Geo " e "! % C.L E p (MeV) Geo Reactor Power (TW) KamLAND data with the solar oscillation constraints Geo reactor power < 6. TW (90% C.L.)

27 Future Prospects (Solar Phase)

28 Neutrino from the Sun pp chain CNO cycle 98.5% 99.77% pp De+ νe (pp) 13.8% 3! ~! -5 % N"13 C + e + + $ e p+13 C"14 N + #! He p 4 He e+ νe (hep) 0.0% Be e 7 Li νe (γ) ( 7 Be) 7 p+14 N"15 O + #! 3 He 3 He 4 He p p 7 13 He 4 He 7 Be γ 13.78% p+1 C"13 N + # 0.3% (pep) Dp 3 He γ 84.7% 3 pe p Dνe 15 O"15 N + e + + $ e!! Be p 8 B γ Li p 4 He 4 He 8 B 8 Be e+ νe ( 8 B) 4 p+15 N"16 O + # p+15 N"1 C + %! 7 ~ 4 & -4! - Solar neutrinos are produced by nuclear fusion reactions in the sun - Small fraction from the CNO cycle (no direct measurement by neutrinos) 17! F"17 O +e + + $ e p+17 O"14 N + %! He 4 He p+16 O"17 F + #!! Solar image by neutrino (Super-Kamiokande)

29 Standard Solar Model - New abundance model strongly disagree with helioseismological measurement - Precise nuclear cross section 3 He(α, γ) 7 Be 14 N(p, γ) 15 O LUNA result : J.N. Bahcall and A.M. Serenelli, Astro. Phys. J. 61, 85 (005) GS98 AGS05 -% -38% S34 :.5% S1,14 : 8.4% KamLAND will measure 7 Be and CNO solar neutrinos and test the lower abundance of heavy element (AGS05)

30 Solar Neutrino Observation KamLAND singles spectra 7 Be ν pep / CNO ν 7 Be ν observation B.G. reduction requirement ~ 1 µbq / m 3

31 Purification of Liquid Scintillator distillation method separation of substances based on boiling point differences ~ milli-liter system ~ liter system real system ~ 1.5 kilo-liter / hour

32 1st Purification (007) - Total 1699 m 3 of LS was purified through Aug. 1, Purified volume / KamLAND volume = 1.4 top region Reduction efficiency is not sufficient

33 nd Purification (008) Improvement of purification (1) Avoid mixing of Liquid Scintillator - precise control of LS density and temperature - boundary monitoring by onsite analysis tool () Find gas leakage in distillation system and detector - Fixed some leakage points at PPO distillation tower and near top of the detector (3) Upgrade of PPO tower for better performance - Low pressure (low temperature) distillation gives efficient removal of impurities in LS We started the nd purification in June Total purified volume (~ Aug. 31) = 1,00 m 3

34 nd Purification Status LS filling purification system - We can keep the LS boundary by the precise density control - The 85 Kr background was reduced by almost two orders of magnitude for full volume LS circulation ~ 1,00 m 3 need ~ a few more cycle?

35 Summary KamLAND improved sensitivity to ν e observation. data-set : 766 ton-yr 881 ton-yr E threshold :.6 MeV 0.9 MeV syst. uncertainty : 6.5% 4.1% In the reactor neutrino analyses, we showed - Oscillatory shape ~ cycle of neutrino oscillation. - Exclusion of LMA II and 0 at more than 4σ C.L. - Precise measurement of oscillation parameters. Geo neutrino flux was measured with better precision. We started the nd purification in June (total purified volume = 1,00 m 3 ), it is going on, and the B.G. reduction status will be reported soon. (α, n) B.G. uncertainty : 3% % (ground state) 0% 0% (excited state)