1 / 58

KamLAND Update

KamLAND Update. Fermi National Accelerator Laboratory January 16, 2007. Lauren Hsu Lawrence Berkeley National Laboratory. Outline. I. Reactor Experiments & Neutrino Oscillations II. KamLAND overview III. KamLAND Results iV. The Future of KamLAND. The Solar Neutrino Problem.

anika
Download Presentation

KamLAND Update

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. KamLAND Update Fermi National Accelerator Laboratory January 16, 2007 Lauren Hsu Lawrence Berkeley National Laboratory

  2. Outline I. Reactor Experiments & Neutrino Oscillations II. KamLAND overview III. KamLAND Results iV. The Future of KamLAND

  3. The Solar Neutrino Problem Chlorine Experiment Homestake Mine Pre-1950: p-p chain 4p  4He + 2e+ + 2e 1968: Ray Davis pioneers the radiochemical experiment, Chlorine, and observes 1/3 of predicted solar neutrino flux. 1969: Pontecorvo and Gribov propose that neutrinos oscillate but… …difficulty of Chlorine experiment and uncertainties in solar model lead to speculation that either one or both were wrong.

  4. 3 Decade Long Mystery 1998: SuperKamiokande announces evidence for oscillations in atmospheric neutrinos nucl-ex/0502021 2001: SNO w/ sensitivity to both (e) and (x) measures total flux of x, consistent with Standard Solar Model

  5. Neutrino Oscillations oscillations imply neutrinos have mass! 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 e-i /2 0 0 0 ei /2 0 0 0 1 1  2 Majorana phases Like quarks, neutrino flavor and mass eigenstates are not the same Simplified expression for two flavor oscillations in a vacuum: P(ll’) = sin22 sin2(1.27m2(eV2)L(m)/E (MeV))

  6. Why a Reactor Neutrino Experiment? Complimentary to the Solar Experiments No matter effects Well-understood man-made source Anti-neutrino vs neutrino oscillations 1955 Reines & Cowan (Poltergeist) Basics • Disappearance Experiment • Detect anti neutrino via inverse beta-decay • Energy range ~few MeV • Reactor anti-neutrino experiments performed since 1950’s

  7. Anti-Neutrino Production in Reactors 235U + n  X1 + X2+ 2n • Anti-neutrinos from beta decay of daughter isotopes • Production of anti-neutrinos well understood theoretically and fission yields • precisely monitored by power companies Calculated spectrum verified to 2% accuracy by earlier generation of reactor anti-neutrino experiments (unoscillated)

  8. KamLAND

  9. Why KamLAND? KamLAND Optimizations: Long Baseline – optimizes sensitivity to oscillations Large (1 kTon!) – combats 1/R2 drop-off in intensity More Overburden: Avoids Cosmogenic Backgrounds

  10. 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

  11. Physics Reach of KamLAND Nature 436, 499 (2005) n-Disappearance hep-ex/0512059

  12. The KamLAND Detector (1879)

  13. 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

  14. 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

  15. 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.

  16. e + p  e+ + n e - e energy obtained from E = Eprompt + 0.8 MeV Anti-Neutrino Signal Detection Coincident energy deposits are a distinct signature of inverse beta-decay:  Prompt Energy: positron energy deposit (K.E. + annihilation ’s) 2.2 MeV e+  n Delayed Energy: n-capture releases 2.2 MeV , ~200 s later

  17. Basic KamLAND Data Reconstruction How much energy deposited and where? • Energy Reconstruction: • Energy  Number of Hit PMT’s • Correction for Vertex Position • Correction for Quenching and • Cherenkov Radiation KamLAND Event Display • Vertex Reconstruction • Determined by Very Precise Timing of Hits (~ few ns): • Inherent Detector Resolution ~15cm.

  18. Calibration Radioactive Sources: Co60, Ge68, Zn65, and AmBe deployed along the z-axis. Backgrounds: Spallation Products throughout fiducial volume

  19. Muon Tracking Source of cosmogenic backgrounds Rate of Muons hitting KamLAND is ~1 Hz • Timing of inner detector hits • Good agreement with • simulation of muons passing • through detailed mountain • topography

  20. Spallation Products Muons interact with material producing fast neutrons and delayed neutron  - emitters Correlated Cosmogenic Backgrounds He8 thought to be a negligeable contribution

  21. Uncorrelated Backgrounds Lots of steel in the chimney region! Uncorrelated backgrounds: • From radioactive isotopes • in detector and surrounding • material. • Activity concentrated near • balloon Reduced by fiducial volume and energy cut. Remaining accidental backgrounds are easily measured

  22. 13C(,n)16O Background low energy ~6 MeV 4.4 MeV Background Prompt E (MeV)

  23. KamLAND Reactors Total reactor power uncertainty in analysis is 2% (conservative estimate)

  24. III. KamLAND Results

  25. First Result: Disappearance 145 live-days (7 months) of data-taking: PRL 90 (2003) 021802 99.95% CL - KamLAND is the first reactor experiment to observe edisappearance!

  26. Second Result: Spectral Distortion 515 live days, better optimized cuts, discovery of 13C background PRL 94 081802 (2005) 258 events observed 365 expected 11% C.L. for best-fit oscillation paramters 0.4% C.L. for scaled no-oscillations spectrum

  27. 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))

  28. +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)

  29. - reactor - e background - Pioneering Search for Geological e Decay of U, Th expected to generate 16 out of ~30-40 TW of Earth’s radiated heat Geological structure of Earth (core, mantle and crust) Geoneutrino sensitivity of KamLAND Th + U signal Radioactive isotope decays produce same signal as reactor e, but at lower energy -

  30. Candidate Events --238U signal -- 232Th signal -- reactor BG --13C BG --accidental BG Expected Spectra w/ extended x-axis Total Background

  31. +26.2 - 23.5 Observed signal = 28 (at 90% C.L.) Geoneutrino Results theoretical prediction Results set an upper limit of 60 TW on the radiogenic power Demonstrating “proof of principle”

  32. IV. The Future of KamLAND

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

  34. Off-axis calibration to improve energy and vertex estimation • Reduce fiducial volume uncertainty Testing 4 at LBNL Using relative distances between sources, expect fiducial volume uncertainty of 1-2%. Full Volume Calibration Full volume calibration system commissioned in July 2006!

  35. Since July: ~200 hrs of 4 data 5 sources 4  positions 3 operators A Typical Day of Off-Axis Calibration In January: 2 more sources additional  more boundary positions

  36. Muon Tracker Gold-plated muon events to cross-check the muon track reconstruction. Module and Frame Testing Testing at LBNL

  37. A Full-Detector Simulation Geant4 visualization of KamLAND Geometry Includes Full Light Propagation Model reflected light laser light indirect light reduce systematic uncertainty increase understanding of detector model backgrounds

  38. Shika II Effect Second Unit at Shika Power Station commissioned May 2005 Impact on baseline depends on the oscillation parameters! Thermal Power (GW)

  39. Projected Future Sensitivity KamLAND will continue to make the most sensitive measurements on m2 for the forseeable future 12

  40. Papers In the Works • KamLAND “First Phase” Paper • Includes all data up to purification • geo, reactor, and high-energy antineutrinos • includes 4 data High Energy B8 Solar Neutrinos NIM Detector Paper Spallation Paper

  41. Be7: KamLAND Low-Background Phase • Verification of low energy neutrino flux from Sun • Observe transition from vacuum to matter-enhanced oscillations • Significantly reduce bg in reactor and geoneutrino analyses KamLAND

  42. An Ambitious Purification Project Detecting e via elastic Scattering (no coincidence to suppress radioactive backgrounds) reduce 210Pb by 5 orders of magnitude! reduce 85Kr by 6 orders of magnitude!

  43. New Distillation System 1.5 m3/hr Purification system commissioned in October 2006 circulation from KamLAND to begin ~next week

  44. KamLAND: First experiment to observe disappearance of reactor • anti-neutrinos (99.998% significance). • Latest results (2004) show evidence for spectral distortion. • Combined solar-experiment and KamLAND results give • m2 = 7.9 10-5eV2 and tan2 = 0.40 +0.6 -0.5 +0.10 -0.07 12 12 Summary • 4 off-axis calibration device commissioned in July, ~200 hrs data taken • will reduce fiducial volume systematic uncertainty. Further improvements to reactor measurement still to come… Phase II of KamLAND: 7Be neutrinos from the sun. Purification starting and low-background measurements to start in 2007.

  45. Tohoku U. LBNL Stanford CalTech KSU U. of TN U. of AL TUNL Drexel U. of NM U. of HI IHEP CENBG Acknowledgements Toyama Oct. 2006 Many pieces of this talk borrowed liberally from my KamLAND colleagues

  46. Mozumi 4/05 KL Control Room to Kamioka Mine

  47. Earlier Reactor Experiments Pre-KamLAND, no oscillations found (baselines 1 km) These experiments demonstrate it can be done.

  48. Energy Estimation Correcting for Nonlinearity of Energy Scale - Only observe e above 3.4 MeV (Eprompt = 2.6 MeV)

  49. Sampling of -Oscillation Experiments By no means comprehensive! Reactor (KamLAND) 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 -

  50. Physics Implications for the First Result

More Related