1 / 73

Recent Results from KamLAND

Recent Results from KamLAND. R. D. McKeown Caltech. BNL – January 17, 2006. Outline. Historical Introduction Neutrino physics Neutrino mixing and oscillations KamLAND reactor neutrino results Geoneutrinos Future prospects. Discovery of the Neutrino – 1956.

bao
Download Presentation

Recent Results from KamLAND

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Recent Results from KamLAND R. D. McKeown Caltech BNL – January 17, 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. 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

  5. Super-Kamiokande Results

  6. Two Generation Model 1.24 (Peg minimum)

  7. Missing solar neutrinos…

  8. n2 n1 Matter Enhanced Oscillation (MSW) Mikheyev, Smirnov, Wolfenstein

  9. Maki – Nakagawa – Sakata Matrix CP violation

  10. Pre – KamLAND summary • Persistent observations of deficit of solar neutrinos • 1998 – observation of oscillations of atmospheric neutrinos by Super-K • 2002 – SNO results imply matter-dependent oscillations of solar neutrinos Time to get our feet on the ground!!

  11. W.A. Fowler Nobel Lecture, 1983

  12. We need a “laboratory” Experiment!!

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

  14. 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

  15. 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

  16. The Reactor Neutrino Flux and Spectrum Reactor Isotopes ~ 200 MeV per fission ~ 6 e per fission ~ 2 x 1020e/GWth-sec • 235U, 239Pu, 241Pu from b measurements • 238U calculated • Time dependence due to fuel cycle

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

  18. Negative Oscillation Searches 103 Distance (m)

  19. (From PDG) The BIG picture: SK atm (nmgnt)

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

  21. 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

  22. 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%

  23. Spectrum Distortion

  24. 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)

  25. The KamLAND Collaboration

  26. 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

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

  28. 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

  29. 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

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

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

  32. Estimate of total volume and fiducial fraction

  33. 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

  34. Radioactivity inside Liquid Scintillator

  35. 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%

  36. 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

  37. 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. Time Variations of Reactor Power and Signals

More Related