a. tsirigotis hellenic open university
DESCRIPTION
A. Tsirigotis Hellenic Open University. N eutrino E xtended S ubmarine T elescope with O ceanographic R esearch Reconstruction, Background Rejection Tools and Methods. Background Sources. Bioluminescence Activity. PMT Rates vs Time : Up-Looking PMTs. Background Sources. - PowerPoint PPT PresentationTRANSCRIPT
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A. TsirigotisA. TsirigotisHellenic Open Hellenic Open
UniversityUniversity
NNeutrino eutrino EExtended xtended SSubmarine ubmarine TTelescope with elescope with
OOceanographic ceanographic RResearchesearch
Reconstruction, Background Reconstruction, Background Rejection Tools and MethodsRejection Tools and Methods
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PMT Rates vs Time : Up-Looking PMTs
Bioluminescence Activity
Background Sources
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PMT Rates vs Time : Down-Looking PMTs
Bioluminescence Activity
Background Sources
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Bioluminescence Activity
Background Sources
•Light Bursts with duration 1-10sec
•Site depended
•Decreases exponentially with depth
•Seasonal variations
•Correlated with water currents
•Contributes to detector dead time
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Number of Collected P.E.s During Bioluminescence Activity
Bioluminescence Activity ExcludedTrigger: ≥ 4fold Coincidence
Bioluminescence Activity
Background Sources
Emitted light at the single photoelectron level
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Bioluminescence Contribution to the Total Trigger Rates
Total Trigger Rates
Bioluminescence Contribution to the Total Trigger Rates
Experimental Trigger Rates from Periods Without Bioluminescence
Bioluminescence Occurs for the 1.1% ± 0.1% of the Active Experimental Time
Bioluminescence Activity
Background Sources
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Data Collected with
4fold Majority Coincidence Trigger
Thresholds at 30 mV
Thresholds at 120 mV
Measured Total Trigger
Rates
(greater or equal to 4fold)
2.61 ± 0.02 Hz 0.12 ± 0.01 Hz
M.C. Prediction
(atmospheric muons only)
0.141 ± 0.005 Hz 0.12 ± 0.01 Hz
Background SourcesK40 beta decay
Increasing Thresholds does not affect seriously the detection efficiency
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single p.e.
LED Run
single p.e. pulse height distribution
two p.e.s pulse height distribution
dark current pulse height distribution
sum of the above
Data from a depth of 4000 m: PMT Pulse Height DistributionCalibration
Background SourcesK40
K40 radioactivity can be used for calibration purposes in deep sea
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Depth intensity curve
Background SourcesCosmic ray muon background Atmospheric muon angular distribution
Okada parameterization
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Background SourcesCosmic ray muon background
Down coming atmospheric muons can be misreconstructed as upcoming neutrino induced muons (mirror tracks)
By using the accumulated charge on each PMT we can reduce the mirror track background
(the reduction depends on the available degrees of freedom)
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Detector Preparation
Attenuation Correction
Reference waveform
Coaxial cable
Electronic delay lines and amplifier
Fourier Transform-Comparison
Frequency (MHz)
Frequency (MHz)
Ph
ase
(rad
)A
mp
litu
de
Signal processing
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Sample
AD
C C
oun
ts
40 MHz Clock Waveform Capture
Event by Event Sampling Interval Variation (Constant Temperature)
RMS=0.006 ns
Time (ns)
Software to Hardware Trigger Time Difference (arbitrary time offset)
σ=0.7ns
Signal processing
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Signal processing
Frequency (MHz)
Frequency (MHz)
Ph
ase
(rad
)A
mp
litu
de
raw data
baseline subtraction
attenuation correction
Off
s et
(AD
C c
oun
ts)
Sample
AT
WD
co
un
ts
ATWD sample number
Vo
ltag
e (
mV
)
Time (ns)
Vo
ltag
e (
mV
)
Time (ns)
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Signal processing V
olta
ge
(m
V)
Time (ns)
Vo
ltag
e (
mV
)
Time (ns)
Before the F.F.T and the attenuation corrections
After the F.F.T and the attenuation corrections
Time (ns)
Vol
tage
(m
V)
Rise Time
16 ns
9 ns
Double pulse disentangling Correction for overflow
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Signal processing
Arrival time definition…
Arrival time
Vo
ltag
e (
mV
)
Time (ns)
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LED Calibration Data
Gain Monitors
Data from a depth of 4000 mCalibration Run
Time Difference (ns)
Nu
mb
er o
f E
ven
tsN
um
ber
of
Eve
nts
Time Difference (ns)
<Δt>: 0.6 ± 0.1 ns
σ : 3.3 ± 0.1 ns
<Δt>: 0.2 ± 0.1 ns
σ : 3.3 ± 0.1 ns
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Data from a depth of 4000 m: Calibration Run
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Reconstructed Waveforms
Input to the Fitter
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Track Reconstruction. . .
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Run: 81_127 Event: 1789
Input to the Fitter
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Run: 81_127 Event: 1789
Fit ResultsBest fit
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Run: 81_127 Event: 1789
Pictorial Representation
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PreliminaryPreliminaryPreliminaryPreliminary
Data
σ=0.94±0.2
M.C. Prediction (atmospheric muons)
Data Points
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PreliminaryPreliminaryTotal number of p.e.s per TrackTotal number of p.e.s per Track
M.C. Prediction (atmospheric muons)
Data Points
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PreliminaryPreliminary
Zenith Angular DistributionZenith Angular Distribution
• χ2 probability > 0.1
• track selection according to the charge-likelihood
• more than 4.5 p.e.s per hit per track
M.C. Prediction (atmospheric muons)
Data Points
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Extension to many floors
•Each floor runs independently (floor sub-event)
•An event is a collection of several floor sub-events when certain
requirements (e.g. timing) are fullfilled
• Online event-building
•Offline track reconstruction
Many Towers
• Track segment fit: using the PMT’s of each Tower
• Global fit: using matched track segments.
•Second iteration to collect more points
One Tower
Trivially the best strategy is to use all the PMT’s independent of tower
This is depended on the trigger, data transmission (e.g. optoelectronics)
and DAQ architecture
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Event 2213 – Run 78 – BFile 70
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Event 2213 – Run 78 – BFile 70
Best Fit
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Event 2213 – Run 78 – BFile 70