Recent Results from KamLAND

1. Recent Results from KamLAND R. D. McKeown Caltech IHEP – June 12, 2006

2. Outline • Historical Introduction Neutrino physics Neutrino mixing and oscillations • KamLAND reactor neutrino results • Geoneutrinos • Future prospects

3. Discovery of the Neutrino – 1956 F. Reines, Nobel Lecture, 1995

4. Pauli (1933) Connection to Parity Nonconservation?

5. Subsequent History • 60’s and 70’s – n became the darling of accelerator-based particle physics ne≠ nm • 1968 – 1st solar n anomaly evidence • 1980’s – new interest in neutrino oscillations (F. Reines, …..) • 1980-present: the quest for neutrino oscillations • 1998 – evidence from Super-K

6. W.A. Fowler Nobel Lecture, 1983

7. We need a “laboratory” Experiment!!

8. Maki – Nakagawa – Sakata Matrix CP violation

9. Enter • Long Baseline (180 km) • Calibrated source(s) • Large detector (1 kton) • Deep underground (2700 mwe)

10. Neutrino Oscillation Studies with Nuclear Reactors • ne from n-rich fission products • detection via inverse beta decay (ne+pge++n) • Measure flux and energy spectrum • Improve detectors, reduce background • Variety of distances L= 10-1000 m

11. g 2.2 MeV d + p e n n g g 511keV 511keV Detection Signal Coincidence signal: detect • Prompt: e+ annihilation g En=Eprompt+En+0.8 MeV • Delayed: n capture 180 ms capture time

13. Reactors are calibrated sources of n ’s !! Precise Measurements Flux and Energy Spectrum g ~1-2 %

14. (From PDG) SK atm (nmgnt)

15. Kashiwazaki Takahama Ohi KamLAND uses the entire Japanese nuclear power industry as a long­baseline source

16. Many reactors contribute to the antineutrino flux at KamLAND *Eν>3.4MeV (Eprompt>2.6MeV) Detailed power and fuel Composition calculation used From electrical power Japanese average fuel used

17. A limited range of baselines contribute to the flux of reactor antineutrinos at Kamioka Korean reactors 3.4±0.3% Rest of the world +JP research reactors 1.1±0.5% Japanese spent fuel 0.04±0.02%

18. Spectrum Distortion

21. Front End Electronics Waveforms are recorded using Analog Transient Waveform Digitizers (ATWDs), allowing multi p.e. resolution Blue: raw data red: pedestal green: pedestal subtracted • The ATWDs are self launching with a threshold ~1/3 p.e. • Each PMT is connected to 2 ATWDs, reducing deadtime • Each ATWD has 3 gains (20, 4, 0.5), allowing a dynamic range of ~1mV to ~1V ADC counts (~120 mV) Samples (~1.5ns)

22. The KamLAND Collaboration

23. KamLAND:timeline • Summer 2000 PMT installation • Jun-Sept 2001 Fill Liquid Scintillator • Jan, 2002 Begin Data Taking • Dec, 2002 Report 1st Physics Results • Jun 2004 Report 2nd Reactor  Results • Sept 2005 Report geoneutrino evidence

24. Energy Determination & Resolution DE/E ~ 6.2% /√E , Light Yield ~ 300p.e./MeV DEsyst = 2.0% at 2.6 MeV

25. Tagged cosmogenics can be used for calibration τ=29.1ms Q=13.4MeV 12B 12N τ=15.9ms Q=17.3MeV μ Fit to data shows that 12B:12N ~ 100:1

26. Energy calibration uses discrete γ and 12B/12N n-p n-12C 68Ge 60Co 65Zn Carefully include Birks law, Cherenkov and light absorption/optics to obtain constants for γ and e–type depositions σ/E ~ 6.2% at 1MeV

27. Vertexing is performed using timing from the 17” PMTs -60 (2.6MeV) Am/Be(~8MeV) -65 (1.1MeV) -68 (1.0MeV) z

28. Monitoring Detector Stability

30. Fraction of volume inside the fiducial radius verified using μ-produced 12B/12N and n (assumed uniform) 12B/12N neutrons

31. Estimate of total volume and fiducial fraction

32. Singles Background Source:Measured:Predicted 14C:? 210Pb: 102Hz:-- High Energy (e.g. μ): 0.33Hz:0.33Hz 85Kr: 606 Hz:-- 40K:1.9Hz:2.1Hz 208Tl: 3.2Hz:1.4Hz 232Th, cosmogenic: 0.19Hz

33. Radioactivity inside Liquid Scintillator

34. Selecting antineutrinos, Eprompt>2.6MeV 5.5 m fiducial cut • - Rprompt, delayed < 5.5 m • - ΔRe-n < 2 m • - 0.5 μs < ΔTe-n < 1 ms • 1.8 MeV < Edelayed < 2.6 MeV • 2.6 MeV < Eprompt < 8.5 MeV • Tagging efficiency 89.8% (543.7 ton) Balloon edge • …In addition: • 2s veto for showering/bad μ • 2s veto in a R = 3m tube along track • Dead-time 9.7%

35. 99.998% CL Observed Event Rates 2002-4 dataset 766.3 ton•yr, Eprompt > 2.6 MeV Observed: 258 events No-oscillation: 365.2 ± 23.7 events Background 17.6 ± 7.2 events accidental 2.69 ± 0.02 9Li/8He (b, n) 4.8 ± 0.9 fast neutron < 0.89 13C(a,n) 10.0 ± 7.1

36. Nobs – NBG Nno-osc =0.658 ± 0.044 (stat) ± 0.047 (syst) Evidence for Reactor ne Disappearance 99.998 % C.L.

38. Solar n: Dm2 = 5.5x10-5 eV2 sin2 2Q = 0.833 G.Fogli et al., PR D66, 010001-406, (2002) Ratio of Measured and Expected ne Flux from Reactor Neutrino Experiments

39. Oscillation Effect

40. KamLAND best fit : Dm2 = 7.9 x 10-5 eV2 tan2q = 0.45

41. Neutrino Mixing • Neutrino Masses • Flavor Oscillations +

42. Combined fit with solar neutrino data Dm2=7.9+0.6-0.5x10-5 eV2 tan2q=0.40+0.10-0.07

43. Solar Neutrino Results Open circles: combined best fit Closed circles: experimental data

45. Geoneutrinos • U/Th/K in crust/mantle - amount of activity - distribution • Energy budget – heat generation - plate tectonics - magnetic field • Structure of earth’s core - constrain models - georeactor?

46. KamLAND Data 13C(a,n) Reactor n Randoms U Th

47. KamLAND Future • Precision Reactor Neutrino Measurements • - 4p calibration system • - refine analysis methods • - more statistics • Supernova detection • Precision Solar Neutrino Measurements • - radiopurity • - low energy threshold • More precise geoneutrino measurement