Download - KamLAND Update
KamLAND Update
Lauren HsuLawrence Berkeley National Laboratory
June 17, 2005
LEPP Journal Club
KamLAND Update - Lauren Hsu
I. Introduction
II. 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
Outline
KamLAND
Inside the Kamioka Mine
KAMioka Liquid scintillator Anti-Neutrino Detector
Surrounded by 53 Japanese Nuclear Reactors
Detecting reactor anti-neutrinos 1 km beneath Mt. Ikeyama
KamLAND Update - Lauren Hsu
Physics Reach of KamLAND
KamLAND Update - Lauren Hsu
The KamLAND Collaboration
Tohoku U.
LBNLStanfordCalTechKS State U.U. of TNU. of ALTUNLDrexel U. of NMU. of HI
IHEP
CENBG
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:
Simplified expression for two flavor oscillations in a vacuum:
P(ll’) = sin22 sin2(1.27m2(eV2)L(m)/E (MeV))
UMNSP =
oscillations imply neutrinos have mass!
1 0 00 e-i/2 00 0 e-i(/2+)
cos12 sin12 0-sin12 cos12 0 0 0 1
1 0 00 cos23 sin23
0 -sin23 cos23
cos13 0 e-isin13
0 1 0-e-isin13 0 cos13
Solar and KamLAND Atmospheric Future reactor oraccelerator
Majorana phases
KamLAND Update - Lauren Hsu
Sampling of -Oscillation Experiments
Reactor(KamLAND)
tan12 & m 12
e disappearance+ appearance
Energy: ~5-15 MeV
Baseline: 1.5108 km
By no means comprehensive!
m23 & sin223
v (?) disappearance
Energy: ~ GeV
Baseline: 15 -13,000 km
2
m23 & sin223
vu (?) disappearance
Energy: ~ GeV
Baseline: 250 km
2
m12 & sin212
e disappearance
Energy: few MeV
Baseline: 180 km
-
22
KamLAND Update - Lauren Hsu
Neutrino Mass Heirarchy
m2
?
e
0.0
m21
m22
m23
m12
m23= (1-3)10-3 eV2
= (7.90.06)10-5 eV2
atmospheric
Solar and KamLAND2
2
Normal or Inverted?
KamLAND Update - Lauren Hsu
Reactor Anti-Neutrino Experiments
• 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 effectsMan-made source
Opportunity to study anti-neutrino vs neutrino oscillations
Basics
KamLAND Update - Lauren Hsu
Anti-Neutrino Production in Reactors
Net thermal power output by all Japanese Nuclear Reactors is 200 GW.
• 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)
Averaged Relative Fission Yields:
235U:238U:239Pu:241Pu = 0.563: 0.079: 0.301:0.057
235U + n X1 + X2 + 2n
No need for a near detector to monitor flux!
KamLAND Update - Lauren Hsu
Un-Oscillated Reactor Neutrino Spectrum
Verified to 2% accuracy by earlier generation of reactor anti-neutrino experiments
Why KamLAND?
More Overburden: Avoids Cosmogenic Backgrounds
Long Baseline – optimizes sensitivity to oscillations
Large (1 kTon!) – combats1/R2 drop-off in intensity
KamLAND sees ~1 anti-neutrino event/day at an effective baseline of 180 km.
KamLAND Optimizations:
KamLAND Update - Lauren Hsu
The First KamLAND Result
PRL 90 (2003) 021802Before KamLAND
KamLAND is the first reactor experiment to observe e disappearance!-
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
• 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).
• Separates target LS volume from buffer oil• 135 m Nylon/EVOH (ethylene vinyl alcohol copolymer)• Supported by kevlar ropes
Liquid Scintillator:
Balloon:
Welding the Balloon
KamLAND Update - Lauren Hsu
KamLAND Photo-Multipliers
• 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
PMT and acrylic panel installation
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
Anti-Neutrino Signal Detection
Coincident energy deposits are a distinct signature of inverse beta-decay:
e + p e+ + n
Delayed Energy: n-capture releases 2.2 MeV , ~200 s later
Prompt Energy: positron energy deposit (K.E. + annihilation ’s)
KamLAND Update - Lauren Hsu
Selecting Candidate Events
Candidate Coincidence Events: t = [0.5, 1000]s
Apply Time and Spacial Cuts to Obtain Candidate Coincidence Events
e energy obtained from E = Eprompt + 0.8 MeV-
KamLAND Update - Lauren Hsu
Basic KamLAND Data Reconstruction
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.
How much energy deposited and where?
KamLAND Update - Lauren Hsu
Energy Calibration
KamLAND Update - Lauren Hsu
Energy Estimation
Only observe e above 3.4 MeV(Eprompt = 2.6 MeV)
Correcting for Nonlinearity of Energy Scale
-
Muon Tracking
Reconstruction of Tracks:• Pattern recognition based on expected timing of inner detector hits• Good agreement with simulation of muons passing through detailed mountain topography
Rate of Muons hitting KamLAND is ~1 Hz
KamLAND Update - Lauren Hsu
Uncorrelated Backgrounds
• From radioactive isotopes in detector and surrounding material. • Activity concentrated near balloon• Fiducial volume cut defined at r = 5.5m
Uncorrelated backgrounds:
Lots of steel in the chimney region!
KamLAND Update - Lauren Hsu
Correlated Cosmogenic Backgrounds
Muons interacting with material produce neutrons and delayedneutron - emitters
Spallation Products
He8 thought to be a negligeable contribution
KamLAND Update - Lauren Hsu
13C(,n)16O Background
low energy
4.4 MeV
~6 MeV
Background Prompt E (MeV)
KamLAND Update - Lauren Hsu
KamLAND Reactors
Total reactor power uncertaintyin analysis is 2%(conservative estimate)
KamLAND Update - Lauren Hsu
Dip in Nuclear Power Output
KamLAND
no
-osc
rat
e e
eve
nts
/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 observed365 expected
KamLAND Update - Lauren Hsu
Looking for Oscillatory Behavior
0.7% goodness of fit1.8% 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
Unparalled Sensitivity to m12
PRL 94 081802 (2005)
2
Extract Oscillation Parameters and Combine with Solar Data
Solar + KamLAND: m12 =7.9 10-5 eV2, tan212 =0.4 2 +0.6-0.5
+0.10-0.07
PR
L 94 081802 (2005)
KamLAND Update - Lauren Hsu
IV. The Future of KamLAND Reactor Measurements
KamLAND Update - Lauren Hsu
Future Improvements: Reactor Analysis
Systematic Unc. on Rate %
Fiducial Volume 4.7
un-oscillated e spectrum (theor.) 2.5
Energy Threshold 2.3
Reactor Power 2.1
Cut Efficiency 1.6
Fuel Composition 1.0
Cross Section 0.2
Livetime 0.06
Total 7.1
Compare to statistical uncertainty: 6.7%
Further Improvements Require Reducing Systematic Uncertainty!
Better understanding of 13C(,n)16O will also improve shape analysis
KamLAND Update - Lauren Hsu
Full Volume Calibration
• A new full-volume calibration device• Off-axis calibration to improve energy and vertex estimation• Reduce fiducial volume uncertainty
Testing 4 at LBNL
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
Goal: A Tuned Full-Detector SimulationGeant4 visualization of
KamLAND
Helps to reduce systematic uncertaintyfor 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 continueto make the most sensitivemeasurements 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
16 TW of Heat predicted from decay of 238U and 232Th concentrated in earth’s crustTotal Heat radiated by Earth is ~44 TW
surface heat flux measurementsFirst search for geologically produced e!-
KamLAND Update - Lauren Hsu
A Measurable Spectrum Below
2.6 MeV
Th + U signal
reactor - e
background
-
Geo-neutrino analysis is very sensitive to quenched neutronsfrom 13C(,n)16O background
KamLAND Update - Lauren Hsu
Be7 Phase: 2nd KamLAND Phase
KamLAND Update - Lauren Hsu
An Ambitious Purification Project
Detecting e
Via elastic Scattering(no coincidence tosuppress radioactivebackgrounds)
KamLAND Update - Lauren Hsu
Purification R&D
• $10 million must be spent this year • Construction of Purification Hall already begun• 3 Distillation towers will be installed.
Kr removal is through Hebubbling and Kr trap~10-4 achieved
Current R&D shows promising results.
KamLAND Update - Lauren Hsu
Post Purification Goal
KamLAND Update - Lauren Hsu
Timeline for KamLAND
Excavation of new purification chamber started in April and nearly finished.
KamLAND Update - Lauren Hsu
Summary
• KamLAND is the first experiment to observe disappearance of reactor anti-neutrinos (99.998% significance).
• Latest results (summer 2004) show evidence for spectral distortion. combined solar-experiment and KamLAND results give:
m2 = 7.9 10-5eV2 and tan2 = 0.40
• Future reactor measurements will benefit from full-volume calibration, a muon tracker, full-detector Monte Carlo, and purification.
• Expect results soon on geo-neutrinos – the first limit ever for observation of anti-neutrinos produced from the earth.
• Phase II of KamLAND: 7Be neutrinos from the sun. Purification stage is already beginning, and measurements to start in 2007.
+0.6-0.5
+0.10-0.0712 12
KamLAND Update - Lauren Hsu
AcknowledgementsAlmost all pieces of this talk borrowed liberally from
my KamLAND colleagues
Reference:
http://www.ba.infn.it/~now2004/talks/12_09_04/plen/KamLAND.pdf
KamLAND Update - Lauren Hsu
Mozumi 4/05
KL Control Room
to Kamioka Mine