low energy challenges in sk-iii
DESCRIPTION
N eutrino O scillation W orkshop. Low Energy Challenges in SK-III. Michael Smy UC Irvine. Conca Specchiulla, September 11 th 2006. 50kt Water Cherenkov Detector with 11,146 20” f PMTs located in Kamioka mine at 36.43 0 N latitude and 137.31 0 longitude ~ 2,400 m.w.e underground. - PowerPoint PPT PresentationTRANSCRIPT
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Neutrino
Oscillation
Workshop
Conca Specchiulla, September 11th 2006Michael SmyUC Irvine
Low Energy Challenges in SK-IIILow Energy Challenges in SK-III
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• 50kt Water Cherenkov Detector with 11,146 20” PMTs• located in Kamioka mine at 36.430N latitude and 137.310
longitude ~2,400 m.w.e underground
Super-KamiokandeSuper-Kamiokande
• April 1996-July 2001: (SK-I) Accident in November 2001 during maintenance Jan. 2003-Oct. 2005: SK-II (half PMT density) July 2006 – (SK-III)
• many physics topics; solar, atmospheric & accelerator ’s, proton decay Courtesy Y. Oyama
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Super-K Is Repaired!Super-K Is Repaired!
Michael Smy, UC Irvine
began in fall 2005…
…now finished!
Village of Dou near Atotsu Mine Entrance Mozumi Mine Entrance
…despitesomeweatherproblems!
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Conca Specchiula, 11th September 2006
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Motivation for Lower ThresholdMotivation for Lower Threshold
1. Extend Solar Neutrino Recoil Electron Spectrum to 4 MeV
2. Measure Gadolinium neutron captures with high efficiency (effective energy spectrum peaks at 5 MeV)
3. Measure reactor anti-neutrinos above 3 MeV
Michael Smy, UC Irvine
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Solar Neutrino ProblemSolar Neutrino Problem
Michael Smy, UC Irvine
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Solar Neutrino Problem Solar Neutrino Problem Explained by SNO and Explained by SNO and Super-K as Neutrino Super-K as Neutrino Flavor Conversion!Flavor Conversion!
Michael Smy, UC Irvine
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Solar 95%
99.73% KamLAND
Solar+KamLAND
Michael Smy, UC Irvine
Solar Neutrino Oscillation ParametersSolar Neutrino Oscillation Parameters
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Solar Neutrino Future MeasurementsSolar Neutrino Future Measurements• Still missing: oscillation signature!• Lower energy real-time 8B neutrino measurement in
SK-III studies transition from vacuum oscillation to matter-dominated oscillations
Michael Smy, UC Irvine
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How To Lower ThresholdHow To Lower Threshold• Must reduce backgrounds…• Reduced Radon emission due to
blast shields• Reduced Radon due to water flow
change• Software Improvements:
– Event Reconstruction– Event Selection– Background Studies
Michael Smy, UC Irvine
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SK-I: Angular distributionsSK-I: Angular distributions
Rn,
5.0-5.5MeV 5.5-6.0MeV
8.0-8.5MeV
14-20MeV
spallation
e search
Courtesy Y. Takeuchi
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SK-I BackgroundsSK-I Backgrounds
Courtesy M. Nakahata
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How To Lower ThresholdHow To Lower Threshold• Must reduce backgrounds…• Reduced Radon emission due to
blast shields• Reduced Radon due to water flow
change• Software Improvements:
– Event Reconstruction– Event Selection– Background Studies
Michael Smy, UC Irvine
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Vertex Vertex ReconstructionReconstruction
Michael Smy, UC Irvine
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New Vertex Fit: BONSAINew Vertex Fit: BONSAI• Before: Clusfit, Kaifit,
Hayai maximize (choose center of timing window for t0)
• BONSAI: use likelihood; better maximization
n
i
xt
i
i
ex1
2
)(2
2
)(gdn
0)(tof)( txtxt iii
))((pdflog),( 0 xttx i
L
Michael Smy, UC Irvine
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BONSAI Performance in SK-IIBONSAI Performance in SK-II
BONSAI 2.0
BONSAI 2.0
BONSAI 2.0
Clusfit
Clusfit
Clusfit
Kaifit
Kaifit
Kaifit
LINAC v=(-3.9,-0.7,12.0)m5 MeV
LINAC v=(-12.1,-0.7,-0.1)m5 MeV
LINAC v=(-12.1,-0.7,-12.1)m5MeV
Michael Smy, UC IrvineEnergy (MeV)
cm
SK-II Monte Carlo
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BONSAI Performance in SK-IBONSAI Performance in SK-I
BONSAI 2.0
BONSAI 2.0
BONSAI 2.0
Clusfit
Clusfit
Clusfit
Kaifit
Kaifit
Kaifit
LINAC v=(-3.9,-0.7,12.0)m5 MeV
LINAC v=(-12.1,-0.7,-0.1)m5 MeV
LINAC v=(-12.1,-0.7,-12.1)m5MeV
Energy (MeV)
cm
SK-II Monte Carlo
Michael Smy, UC Irvine
Threshold Goal Threshold Goal
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SK-I Reduction: BONSAI Fid. CutSK-I Reduction: BONSAI Fid. Cut
Michael Smy, UC Irvine
These Events already passed 2m dwall
cuts from Hayai (online), Kai-Fit(online), Kai-Fit (offline) & Clusfit(offline) as well as an 8m d cut!!
SK-I: 4.5-5 MeVd
dwall
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Event SelectionEvent Selection(Tested at SK-II)(Tested at SK-II)
Michael Smy, UC Irvine
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Reconstruction Reconstruction QualityQuality
• Timing residual goodness: 0=bad, 1=good
• Direction goodness: azimuthal symmetry 0=good, 1=bad
• Reject non-Cherenkov events and misreconstructed events
Michael Smy, UC Irvine
Good Calibration Events
Low Energy Sample
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Reconstruction Reconstruction QualityQuality
• Timing residual goodness: 0=bad, 1=good
• Direction goodness: azimuthal symmetry 0=good, 1=bad
• Reject non-Cherenkov events and misreconstructed events
• Hyperbolical cut: gt2-
gd2>0.25Michael Smy, UC Irvine
Good Calibration Events
Low Energy Sample
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Solar Peak at SK-II at 7MeVSolar Peak at SK-II at 7MeV
Michael Smy, UC Irvine
Livetime622 Days
Livetime622 Days
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Recoil Electron SpectrumRecoil Electron Spectrum
Michael Smy, UC Irvine
88B B MC only MC only 88B B MC only MC only
8B=2.33x106/cm2shep=15x103/cm2s
MC:
ADN=-1.8±1.6±1.2% ADN=-6.3±4.3%(stat)
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SK-ISK-II SK-I+SK-II
Michael Smy, UC Irvine
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Background StudiesBackground Studies
Michael Smy, UC Irvine
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Lantern Mantle SourceLantern Mantle Source• contains large amounds of 208Tl
• produces 60kBq of 2.6MeV ’s
Michael Smy, UC Irvine
300 Lantern Mantles
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Lantern Mantle Source in SK-IILantern Mantle Source in SK-II
x=-1661.45 cm y=-70.7 cm z=1559.8 cm
>6 MeV
Michael Smy, UC Irvine
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Lantern Mantle Source in SK-IIILantern Mantle Source in SK-III
Michael Smy, UC Irvine
x=-71 cm y=71 cm
z=1830 cm
Clusfit
BONSAI
Clusfit
BONSAI
ClusfitBONSAI Clusfit
BONSAI
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ConclusionsConclusions
• energy threshold of 4 MeV for solar neutrinos is very ambitions for a large water Cherenkov detector…
• …but we learned a lot from SK-II how to live with small # of photo-electrons!– we have better vertex reconstruction– we have a better event selection– we have a better understanding of the backgrounds
Michael Smy, UC Irvine