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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 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 2nd Reactor Analysis III. The Future of KamLAND Reactor Measurements IV. Other Future Measurements: Geo-neutrinos and Be7 KamLAND Update - Lauren Hsu
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
Physics Reach of KamLAND KamLAND Update - Lauren Hsu
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
Role of Reactor Experiments in Neutrino Oscillations KamLAND Update - Lauren Hsu
Neutrino Oscillations Review Like quarks, neutrino flavor and mass eigenstates are not the same: cos12 sin12 0 -sin12 cos12 0 0 0 1 cos13 0 e-isin13 0 1 0 -e-isin13 0 cos13 1 0 0 0 cos23 sin23 0 -sin23 cos23 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(ll’) = sin22 sin2(1.27m2(eV2)L(m)/E (MeV)) oscillations imply neutrinos have mass! KamLAND Update - Lauren Hsu
Reactor (KamLAND) Sampling of -Oscillation Experiments By no means comprehensive! 2 m23 & sin223 v (?) disappearance Energy: ~ GeV Baseline: 15 -13,000 km 2 m23 & sin223 vu (?) disappearance Energy: ~ GeV Baseline: 250 km tan12 & m 12 edisappearance +appearance Energy: ~5-15 MeV Baseline: 1.5108 km 2 2 m12 & sin212 edisappearance Energy: few MeV Baseline: 180 km - KamLAND Update - Lauren Hsu
m2 e m23 m23 m12 m22 ? m21 0.0 Neutrino Mass Heirarchy Normal or Inverted? 2 atmospheric = (1-3)10-3 eV2 2 = (7.90.06)10-5 eV2 Solar and KamLAND KamLAND Update - Lauren Hsu
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
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
Un-Oscillated Reactor Neutrino Spectrum Verified to 2% accuracy by earlier generation of reactor anti-neutrino experiments KamLAND Update - Lauren Hsu
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.
The First KamLAND Result PRL 90 (2003) 021802 Before KamLAND - KamLAND is the first reactor experiment to observe edisappearance! KamLAND Update - Lauren Hsu
Physics Implications for the First Result KamLAND Update - Lauren Hsu
III. KamLAND Overview and Results on 2nd Reactor Analysis KamLAND Update - Lauren Hsu
The KamLAND Detector (1879) KamLAND Update - Lauren Hsu
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
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
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
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
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
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
Energy Calibration KamLAND Update - Lauren Hsu
Energy Estimation Correcting for Nonlinearity of Energy Scale - Only observe e above 3.4 MeV (Eprompt = 2.6 MeV) KamLAND Update - Lauren Hsu
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
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
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
13C(,n)16O Background low energy ~6 MeV 4.4 MeV Background Prompt E (MeV) KamLAND Update - Lauren Hsu
KamLAND Reactors Total reactor power uncertainty in analysis is 2% (conservative estimate) KamLAND Update - Lauren Hsu
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
Looking for Correlations in Un-Oscillated Rate Changes KamLAND Update - Lauren Hsu
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
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
Looking for Oscillatory Behavior 0.7% goodness of fit 1.8% goodness of fit Simplified expression for two flavor oscillations in a vacuum: P(ll’) = sin22 sin2(1.27m2(eV2)L(m)/E (MeV)) KamLAND Update - Lauren Hsu
+0.10 -0.07 +0.6 -0.5 2 Solar + KamLAND: m12 =7.9 10-5 eV2, tan212 =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
IV. The Future of KamLAND Reactor Measurements KamLAND Update - Lauren Hsu
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
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
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
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
A Change in Effective Baseline? Shika upgrade will be complete in 2006. Impact on baseline will depend on the oscillation parameters! (sin212, m2) 12 KamLAND Update - Lauren Hsu
Projected Future Sensitivity KamLAND will continue to make the most sensitive measurements on m2 for the forseeable future 12 KamLAND Update - Lauren Hsu
V. Other Future Measurements: Geo-neutrinos and Be7 KamLAND Update - Lauren Hsu
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
- 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
Be7 Phase: 2nd KamLAND Phase KamLAND Update - Lauren Hsu
An Ambitious Purification Project Detecting e Via elastic Scattering (no coincidence to suppress radioactive backgrounds) KamLAND Update - Lauren Hsu
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
Post Purification Goal KamLAND Update - Lauren Hsu