KamLAND Update

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KamLAND Update
NuFact 05 June 21, 2005

• Lauren Hsu
• Lawrence Berkeley National Laboratory
• For the KamLAND Collaboration

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KamLAND
KAMioka Liquid scintillator Anti-Neutrino
Detector
Looking for disappearance of anti-neutrinos 1 km
beneath Mt. Ikeyama
Inside the Kamioka Mine
Surrounded by 53 Japanese Nuclear Reactors
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The KamLAND Detector
(1879)
2.5 m thick
Liquid Scintillator 20 Pseudocume 80
Mineral Oil 1.5 g/l PPO HC 2
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Anti-Neutrino Signal Detection
Use coincident energy deposits of inverse
beta-decay
Signal Selection ?T 0.5, 1000?s ?R lt
2m rvertex lt 5.5m Eprompt 2.6, 8.5
MeV Edelayed 1.6, 2.6MeV
?e p ? e n
Prompt Energy positron energy deposit (K.E.
annihilation ?s)
Candidate Coincidence Events ?T 0.5, 1000?s
Delayed Energy n-capture releases 2.2 MeV ?,
200 ?s later
-
?e energy E? Eprompt 0.8 MeV
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Energy Estimation
Evis/Ereal
Correcting for Nonlinearity of Energy Scale
60Co, 68Ge, 65Zn, deployed along z
Uniform spallation products off-z
Ereal (MeV)
-
Only observe ?e above 3.4 MeV (Eprompt 2.6 MeV)
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Fiducial Volume Estimate
Events/bin
z deviation (cm)
z-axis (cm)
(R/6.5m)
Fiducial Volume Uncertainty
Flow Meters 0.595 /- 0.013 12B/12N spallation
0.607 ? 0.006 ? 0.006 Energy Dependence
2.7 Total 4.7
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Backgrounds
Correlated 13C(?,n)16O Background Troublesome and
new! ?s produced indirectly through decay of
210Pb, a long-lived daughter of 222Rn
Correlated Muon Spallation Backgrounds fast
neutrons or delayed-n ?-decay of 9Li
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Reactor Flux
Total reactor power uncertainty is 2
(conservative estimate)
Averaged Relative Fission Yields
235U238U239Pu241Pu 0.563 0.079
0.3010.057
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Improvements Over First Result
First KamLAND Result

• 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 to 6/?E(MeV))
• Reactor off-time ? study correlation
• of signal with reactor flux.

PRL 90 (2003) 021802
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Observation of Spectral Distortion
PRL 94 081802 (2005)
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Neutrino Oscillations Favored
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))
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Unparalled Sensitivity to ?m12
2
Extract Oscillation Parameters and Combine with
Solar Data
PRL 94 081802 (2005)
PRL 94 081802 (2005)
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Future Improvements Reactor Analysis
Further Improvements Require Reducing Systematic
Uncertainty!
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
Better understanding of 13C(?,n)16O will also
improve shape analysis
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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
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More Improvements
A Muon Tracker
A Full-Detector Simulation

• Gold-plated events
• 200 events/day
• x-y resolution of 2-3 cm.

A flexible tool for systematic studies.
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A Change in Effective Baseline?
Shika upgrade will be complete in 2006. Impact
on baseline will depend on the oscillation
parameters!
(sin2?12, ?m2)
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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 earths crust Total Heat
radiated by Earth is 44 TW
Th U signal
-
reactor - ?e background
Sorry, no results yet, but paper to be released
soon!
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Future KamLAND 7Be Phase
Detect ?e from 7Be via elastic scattering (not a
coincidence signal)
KamLAND needs to reduce 210Pb and 85Kr by 5-6
orders of magnitude!
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Timeline for KamLAND
Excavation of new purification chamber started
in April and nearly finished.
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Summary

• KamLAND has observed disappearance of reactor
  anti-neutrinos at
• 99.998 significance.
• Latest results (PRL 94 081802 2005) show
  evidence for spectral
• distortion, combined solar and KamLAND results
  give the most precise
• determination to date
• ?m2 7.9 ?10-5eV2 and tan2? 0.40
  
• Future KamLAND measurements to benefit from
  full-volume
• calibration, muon tracker, full-detector
  simulations, and purification.
• Results coming soon on geo-neutrinos the
  first limit or
• 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.

0.10 -0.07
0.6 -0.5
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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

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Looking for Correlations in Un-Oscillated Rate
Changes
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Changes from Extra BG