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KamLAND Update

KamLAND Update. June 17, 2005 LEPP Journal Club. Lauren Hsu Lawrence Berkeley National Laboratory. Outline. Introduction Role of Reactor Experiments in Neutrino Oscillations II. KamLAND Overview and Results on 2 nd Reactor Analysis III. The Future of KamLAND Reactor Measurements

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KamLAND Update

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  1. KamLAND Update June 17, 2005 LEPP Journal Club Lauren Hsu Lawrence Berkeley National Laboratory

  2. Outline • Introduction • Role of Reactor Experiments in Neutrino Oscillations II. KamLAND Overview and Results on 2nd Reactor Analysis III. The Future of KamLAND Reactor Measurements IV. Other Future Measurements: Geo-neutrinos and Be7 KamLAND Update - Lauren Hsu

  3. KamLAND KAMioka Liquid scintillator Anti-Neutrino Detector Detecting reactor anti-neutrinos 1 km beneath Mt. Ikeyama Inside the Kamioka Mine Surrounded by 53 Japanese Nuclear Reactors

  4. Physics Reach of KamLAND KamLAND Update - Lauren Hsu

  5. Tohoku U. LBNL Stanford CalTech KS State U. U. of TN U. of AL TUNL Drexel U. of NM U. of HI IHEP CENBG The KamLAND Collaboration KamLAND Update - Lauren Hsu

  6. Role of Reactor Experiments in Neutrino Oscillations KamLAND Update - Lauren Hsu

  7. Neutrino Oscillations Review Like quarks, neutrino flavor and mass eigenstates are not the same: cos12 sin12 0 -sin12 cos12 0 0 0 1 cos13 0 e-isin13 0 1 0 -e-isin13 0 cos13 1 0 0 0 cos23 sin23 0 -sin23 cos23   UMNSP = Future reactor or accelerator Atmospheric Solar and KamLAND 1 0 0 0 e-i/2 0 0 0 e-i(/2+)  Majorana phases Simplified expression for two flavor oscillations in a vacuum: P(ll’) = sin22 sin2(1.27m2(eV2)L(m)/E (MeV)) oscillations imply neutrinos have mass! KamLAND Update - Lauren Hsu

  8. Reactor (KamLAND) Sampling of -Oscillation Experiments By no means comprehensive! 2 m23 & sin223 v (?) disappearance Energy: ~ GeV Baseline: 15 -13,000 km 2 m23 & sin223 vu (?) disappearance Energy: ~ GeV Baseline: 250 km tan12 & m 12 edisappearance +appearance Energy: ~5-15 MeV Baseline: 1.5108 km 2 2 m12 & sin212 edisappearance Energy: few MeV Baseline: 180 km - KamLAND Update - Lauren Hsu

  9. m2 e   m23 m23 m12 m22 ? m21 0.0 Neutrino Mass Heirarchy Normal or Inverted? 2 atmospheric = (1-3)10-3 eV2 2 = (7.90.06)10-5 eV2 Solar and KamLAND KamLAND Update - Lauren Hsu

  10. Reactor Anti-Neutrino Experiments Basics • Disappearance Experiment • Detect anti neutrino via inverse beta-decay • Energy range ~few MeV • Reactor anti-neutrino experiments performed since 1950’s • Detector relatively simple and basic design unchanged Why a Reactor Neutrino Experiment? No matter effects Man-made source Opportunity to study anti-neutrino vs neutrino oscillations KamLAND Update - Lauren Hsu

  11. Anti-Neutrino Production in Reactors 235U + n  X1 + X2+ 2n • Anti-neutrinos produced in beta decay of daughter isotopes resulting from • fission • Production of anti-neutrinos well understood theoretically and fission yields • precisely monitored by power companies (to 2% uncertainty) No need for a near detector to monitor flux! Averaged Relative Fission Yields: 235U:238U:239Pu:241Pu =0.563: 0.079: 0.301:0.057 Net thermal power output by all Japanese Nuclear Reactors is 200 GW. KamLAND Update - Lauren Hsu

  12. Un-Oscillated Reactor Neutrino Spectrum Verified to 2% accuracy by earlier generation of reactor anti-neutrino experiments KamLAND Update - Lauren Hsu

  13. Why KamLAND? KamLAND Optimizations: More Overburden: Avoids Cosmogenic Backgrounds Long Baseline – optimizes sensitivity to oscillations Large (1 kTon!) – combats 1/R2 drop-off in intensity KamLAND sees ~1 anti-neutrino event/day at an effective baseline of 180 km.

  14. The First KamLAND Result PRL 90 (2003) 021802 Before KamLAND - KamLAND is the first reactor experiment to observe edisappearance! KamLAND Update - Lauren Hsu

  15. Physics Implications for the First Result KamLAND Update - Lauren Hsu

  16. III. KamLAND Overview and Results on 2nd Reactor Analysis KamLAND Update - Lauren Hsu

  17. The KamLAND Detector (1879) KamLAND Update - Lauren Hsu

  18. The Target Volume Liquid Scintillator: • Serves as both the target and the • detector, > 1031 protons • 20% Pseudocume + 80% Mineral Oil • + 1.5 g/l PPO • Optimal light yield while maintaining • long attenuation length (~20 m). Welding the Balloon Balloon: • Separates target LS volume from • buffer oil • 135 m Nylon/EVOH • (ethylene vinyl alcohol copolymer) • Supported by kevlar ropes KamLAND Update - Lauren Hsu

  19. KamLAND Photo-Multipliers PMT and acrylic panel installation • 1325 17” tubes • 554 20” tubes (since • 2/03) • Transit time spread • < 3 ns • Separated from inner • buffer by acrylic • panels • 200 17” hits for 1 MeV • energy deposit KamLAND Update - Lauren Hsu

  20. The Outer Detector • 3.2 kT water Cerenkov detector (~200 • PMT’s) • Detects 92% of muons passing through • inner detector • Buffers inner detector from spallation • products and radioactivity in rock. KamLAND Update - Lauren Hsu

  21. e + p  e+ + n Anti-Neutrino Signal Detection Coincident energy deposits are a distinct signature of inverse beta-decay: Prompt Energy: positron energy deposit (K.E. + annihilation ’s) Delayed Energy: n-capture releases 2.2 MeV , ~200 s later KamLAND Update - Lauren Hsu

  22. Apply Time and Spacial Cuts to Obtain Candidate Coincidence Events Candidate Coincidence Events: t = [0.5, 1000]s - e energy obtained from E = Eprompt + 0.8 MeV Selecting Candidate Events KamLAND Update - Lauren Hsu

  23. Basic KamLAND Data Reconstruction How much energy deposited and where? • Energy Reconstruction: • Energy  Number of Hit PMT’s • Correction for Vertex Position • Corrections for Quenching and • Cerenkov • Vertex Reconstruction • Determined by Very Precise Timing of Hits (~ few ns): • Inherent Detector Resolution ~15cm. • Based on push-pull minimization algorithm. Energy and Vertex fitter Calibrated w/ Co60, Ge68, Zn65, and AmBe deployed along the z-axis. KamLAND Update - Lauren Hsu

  24. Energy Calibration KamLAND Update - Lauren Hsu

  25. Energy Estimation Correcting for Nonlinearity of Energy Scale - Only observe e above 3.4 MeV (Eprompt = 2.6 MeV) KamLAND Update - Lauren Hsu

  26. Muon Tracking Rate of Muons hitting KamLAND is ~1 Hz • Reconstruction of Tracks: • Pattern recognition based on • expected timing of inner • detector hits • Good agreement with • simulation of muons passing • through detailed mountain • topography

  27. Uncorrelated Backgrounds Lots of steel in the chimney region! Uncorrelated backgrounds: • From radioactive isotopes • in detector and surrounding • material. • Activity concentrated near • balloon • Fiducial volume cut defined • at r = 5.5m KamLAND Update - Lauren Hsu

  28. Spallation Products Muons interacting with material produce neutrons and delayed neutron  - emitters Correlated Cosmogenic Backgrounds He8 thought to be a negligeable contribution KamLAND Update - Lauren Hsu

  29. 13C(,n)16O Background low energy ~6 MeV 4.4 MeV Background Prompt E (MeV) KamLAND Update - Lauren Hsu

  30. KamLAND Reactors Total reactor power uncertainty in analysis is 2% (conservative estimate) KamLAND Update - Lauren Hsu

  31. KamLAND Dip in Nuclear Power Output no-osc rate eevents/day Falsified saftey records prompted shutdown of several nuclear power plants KamLAND Update - Lauren Hsu

  32. Looking for Correlations in Un-Oscillated Rate Changes KamLAND Update - Lauren Hsu

  33. What Were Improvements? • More Statistics: 515.1 live days compared to 145.1 live days. • 13C(,n)16O background discovered and included in analysis • Better Optimized Cuts (fiducial volume increased from 5m • to 5.5m) • Addition of 20” tubes (improved energy resolution from • 7%/E(MeV) to 6%/E(MeV)) • Reactor off-time allowed for study of correlation of signal • with reactor flux. Second results includes re-analysis of same data-sample used in first KamLAND Update - Lauren Hsu

  34. Observation of Spectral Distortion from Neutrino Oscillations Measurement of Energy Spectral Distortion Due to Oscillation: PRL 94 081802 (2005) 258 events observed 365 expected KamLAND Update - Lauren Hsu

  35. Looking for Oscillatory Behavior 0.7% goodness of fit 1.8% goodness of fit Simplified expression for two flavor oscillations in a vacuum: P(ll’) = sin22 sin2(1.27m2(eV2)L(m)/E (MeV)) KamLAND Update - Lauren Hsu

  36. +0.10 -0.07 +0.6 -0.5 2 Solar + KamLAND: m12 =7.9 10-5 eV2, tan212 =0.4 Unparalled Sensitivity to m12 2 Extract Oscillation Parameters and Combine with Solar Data PRL 94 081802 (2005) PRL 94 081802 (2005) KamLAND Update - Lauren Hsu

  37. IV. The Future of KamLAND Reactor Measurements KamLAND Update - Lauren Hsu

  38. Future Improvements: Reactor Analysis Further Improvements Require Reducing Systematic Uncertainty! Compare to statistical uncertainty: 6.7% Better understanding of 13C(,n)16O will also improve shape analysis KamLAND Update - Lauren Hsu

  39. Testing 4 at LBNL Full Volume Calibration • A new full-volume calibration device • Off-axis calibration to improve energy and vertex estimation • Reduce fiducial volume uncertainty Source placement uncertainty of 2 cm will measure fiducial volume to 2-3% uncertainty KamLAND Update - Lauren Hsu

  40. A Muon Tracker • Gold-plated muon events will • cross-check the muon track- • reconstruction. • Three layer tracking chamber • prop tubes • ~200 events per day in • coincidence with inner detector • x-y resolution of 2-3 cm. • assembled by graduate • student(s) at LBNL. KamLAND Update - Lauren Hsu

  41. A Full-Detector Simulation Geant4 visualization of KamLAND Goal: A Tuned Full-Detector Simulation Helps to reduce systematic uncertainty for next analysis and increase understanding of detector KamLAND Update - Lauren Hsu

  42. A Change in Effective Baseline? Shika upgrade will be complete in 2006. Impact on baseline will depend on the oscillation parameters! (sin212, m2) 12 KamLAND Update - Lauren Hsu

  43. Projected Future Sensitivity KamLAND will continue to make the most sensitive measurements on m2 for the forseeable future 12 KamLAND Update - Lauren Hsu

  44. V. Other Future Measurements: Geo-neutrinos and Be7 KamLAND Update - Lauren Hsu

  45. Geo-Anti-Neutrinos surface heat flux measurements - First search for geologically produced e! 16 TW of Heat predicted from decay of 238U and 232Th concentrated in earth’s crust Total Heat radiated by Earth is ~44 TW KamLAND Update - Lauren Hsu

  46. - reactor - e background A Measurable Spectrum Below 2.6 MeV Geo-neutrino analysis is very sensitive to quenched neutrons from 13C(,n)16O background Th + U signal KamLAND Update - Lauren Hsu

  47. Be7 Phase: 2nd KamLAND Phase KamLAND Update - Lauren Hsu

  48. An Ambitious Purification Project Detecting e Via elastic Scattering (no coincidence to suppress radioactive backgrounds) KamLAND Update - Lauren Hsu

  49. Purification R&D Current R&D shows promising results. Kr removal is through He bubbling and Kr trap ~10-4 achieved • $10 million must be spent this year • Construction of Purification Hall already begun • 3 Distillation towers will be installed. KamLAND Update - Lauren Hsu

  50. Post Purification Goal KamLAND Update - Lauren Hsu

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