ligo-g050281-00-z status of the ligo-auriga joint burst analysis l. cadonati for the ligo-auriga...
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LIGO-G050281-00-Z
Status of the LIGO-AURIGA Joint Burst Analysis
L. Cadonati for the LIGO-AURIGA joint working group
LSC meeting – Ann Arbor, June 4 2005
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Scope of this talk
Describe “tuning in action” for the first LIGO-AURIGA coincidence search: an all-sky, trigger-based burst search performed over the last two weeks of S3 in coincidence with AURIGA’s run 331.
We use a tuning data set obtained with 49 sets of time lags between AURIGA, LHO and LLO data and discuss how the analysis thresholds affect the final background rate and the detection efficiency for a class of simulated waveforms. We choose here to focus on sine and cosine Gaussians at f0=900 Hz, Q=9.
Francesco Salemi (AURIGA) is planning to present this material at the Amaldi Conference,
on behalf of the LSC and the AURIGA Collaboration
(except for slides marked as “not Amaldi”)
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Sensitivity Spectrasi
ngle
-sid
ed P
SD
best performanceduring the 331 and the S3 run
AURIGA run 331: Dec 24 2003 – Jan 14 2004
LIGO S3 run: Oct 31 2003 – Jan 9 2004
AURIGA 331: poor data quality (unmodeled excess noise)
LIGO S3: glitchy, noise variability
Main scope of analysis of this data set: study of IFO-bar methodologies on actual data.
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Data Selection Criteria
LIGO’s data selection criteria» Applied all data quality flags selected for the LIGO-only analysis (dust
included)» Require all three interferometers in operation
The veto implemented on the AURIGA side to compensate run-specific effects
» Wide-band glitches» Epoch veto based on Monte Carlo detection efficiency
Coincidence run (after removal of 10% playground data set): 352 h
After AURIGA wide-band (4%) and epoch (42%) veto: 211 h
LIGO H1H2-noL1 (with DQ flags): 193 h
Intersection (AU-H1-H2): 116 h
LIGO triple coincidence (with DQ flags): 61 h
Intersection (AU-H1-H2-L1): 36 h
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Analysis methodFrom the white paper:
method 2, “eyes wide open”
No assumptions are made on direction or waveform.
The r-statistic test (within CorrPower ) is applied to the LIGO interferometers around the time of the AURIGA triggers.
Single-IFO hrss at each LIGO detector is estimated with the burst parameter estimation code (Note: this portion of the analysis is not mature for presentation at AMALDI)
Efficiency for classes of waveforms and source population is performed through Monte Carlo simulation, LIGO-style.
The accidental rate (background) is estimated from “off-source” data sets, where LLO and LHO data streams are time-shifted (different lags) with respect to the AURIGA data stream.
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Minimal Thresholds AURIGA: for the analysis of run 331 data, the exchange threshold is as low as allowed
before hitting the Gaussian wall: SNR > 4.5 (empirically chosen). Since the noise performance in run 331 was far from stationary Gaussian, the threshold to be used in an hypothetical IGEC-style search would have been SNR>7.
LIGO: from first principles, events with in Gaussian noise are consistent with the null hypothesis (no correlation) at the 0.1% level or higher: these events can already be discarded. S3 was a “glitchy” run (the LIGO-only used the threshold !); we decided to use as starting point/minimal threshold that of S2 ().
The tuning procedure will establish which direction we need to move away from these minimal thresholds.
The tuning procedure is still in progress: we have explored 4-detector coincidences and are working on the AU-H1-H2 triple coincidence. We reserve to freeze
thresholds after we have explored both sectors and remain blind to the final result until that point.
In order to exemplify the procedure, today we will discuss background and detection efficiency for a sample waveform and a trial set of thresholds and how these
quantity are affected by the thresholds choice.
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Diagnostic plots ofAURIGA triggers
AURIGA trigger generation: delta matched filter.» Events characterized by time, its uncertainty, H, SNR
Rate (SNR>4.5) vs “live hours” in the AURIGA dataset
SNR vs time
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More AURIGA diagnostics
20 sec “bump”
Auto-coincidences (100 ms window)Plateaux reached at ~ 300 secBump at 20 sec disappears increasing the SNR threshold
SNR>7
SNR>6
SNR>5
SNR>4.5
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LIGO events
Apply r-statistic test in CorrPower » Auriga arrival time ± uncertainty ± 27 ms (=flight time)
» Max uncertainty =100ms, typical <<100ms
Use to make a statement on the coherence between the 3 LIGO IFOs.
Impose H1-H2 consistency criteria:» Sign of the H1-H2 correlation
» Amplitude cut between H1 and H2 (800-1000 Hz vs broadband? This is not in a mature state, but is already showing promising results in the rejection of background events)
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Testing correlation of LIGO (lagged) data around the time of AURIGA triggers
A background set reserved for tuning purposes:
49 time lags between AU, LLO and LHO
No H1-H2 consistency cuts applied yet
Triggers below SNR=4.5 are not exchanged
Minimal threshold
1.4 million triggers in the background dataset
~200 triggers above minimal thresholds
AURIGA SNR (red=all blue=AU-H1-H2-L1) LIGO (49 lags, AU-H1-H2-L1)
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Testing correlation of LIGO (lagged) data around the time of AURIGA triggers
(NOT to be shown at Amaldi)
A background set reserved for tuning purposes:
49 time lags between AU, LLO and LHO
No H1-H2 consistency cuts applied yetTriggers below
SNR=4.5 are not exchanged
Minimal threshold
1.4 million triggers in the background dataset
~200 triggers above minimal thresholds
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Tuning the Amplitude Cut (NOT to be shown at Amaldi)
Ratio = max(H1/H2, H2/H1) Ratio = 2 vs ratio = 3: 5% loss in detection efficiency, small gain in falses. Preliminary choice: ratio=3
ratio=3
Red: background events
Black: simulated signals (sine/cosine gaussians, gaussians, damped sinusoids)
ratio=3
≥ 4 ≥ 6
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histograms before and after H1-H2 amplitude cut
(NOT to be shown at Amaldi)
Surviving events are being followed up (glitches at L1,H1 in random coincidence?) amplitude cut promising…
distribution for all background events in the set (1.4 million events)
Surviving R0>0 but not amplitude cut (ratio=3)
Surviving both H1H2 consistency cuts
Events rejected by the R0>0 cut
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Scatter plot of false events before and after H1-H2 amplitude cut
(NOT to be shown at Amaldi)
1.4 million triggers were in the background dataset
3 events left with the preliminary tuning parameters, corresponding to 0.07 events expected at zero lag, 0.5 mHz background rate
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Tuning Summary Plot (2-d ROC) using Sine/Cosine Gaussians
f0=900Hz Q=9
Trial thresholds for illustration
The response is dominated by AURIGA sensitivity/noise: better increase LIGO threshold to suppress falses and preserve efficiency
Background events contour lines 1, 5, 10 evts/49 lags
Preliminary background events contour lines are conservative: ongoing studies of H1-H2 amplitude cut are promising for suppression of false events.
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Preliminary sensitivity
Using the trial tuning parameters:» >6
» SNR_AURIGA>4.5
» No H1-H2 amplitude cut (not yet mature)
Sine/cosine gaussians:» Efficiency of the joint search is dominated by AURIGA
» A factor 2 worse than LIGO-only at similar frequency
» AURIGA alone: sensitivity improved by a factor <2 due to the lower SNR threshold (with the non-gaussianity of the run 331 data set, a threshold of SNR 7-8 would be required by the IGEC protocol)
Tested damped sinusoids and gaussian pulses too – not reported here.
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Efficiency curve for sine/cosine gaussians with trial set of tuning parameters
Tuning tests performed so far indicate that the efficiency curve changes by at most 10% as the tuning parameters are changed in the range that is being considered.
SNR_auriga=4.5
0=6 is not critical for the
efficiency (see tuning plot)
Preliminary studies on the introduction of an H1-H2 amplitude cut would give at most a 5-10% loss in hrss_50.
AURIGA:7.5e-20 Hz-0.5 at SNR=78.5e-20 Hz-0.5 at SNR=8(threshold range required by the IGEC protocol for run 331)
2.3e-20 Hz-0.5
LIGO only at 850HzWaveburst ETG0=10
Efficiency curve for the joint analysis, dominated by AURIGA: 50% efficiency at ~5.5e-20 Hz-0.5
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Outlook
Step needed to complete the “all-sky” S3-331 coincidence analysis:» Complete characterization and implementation of an H1-H2
amplitude cut for false events suppression.
» Repeat analysis of triple coincidence AU-H1-H2
» Fix thresholds and open the box for zero-lag coincidences
Still exploring possibilities for a targeted, directional joint analysis.
LIGO-G050281-00-Z
EXTRA SLIDES
Talk given at GWDAW by LC on behalf of the LIGO-AURIGA joint working group
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MOU for S3/AU1 burst analysis signed in July 2004» develop methodologies for bar/interferometer searches
» implement on real data a time coincidence, triggered based searches
» explore coherent methods
Joint Working Group composition:» AURIGA: G. Prodi, L. Baggio, A. Mion, A. Ortolan, S. Poggi, F. Salemi, G. Vedovato
» LSC: L. Cadonati, S. Heng, W. Johnson, P. Sutton, M. Zanolin
Target analysis completion: spring 2005
AURIGA-LIGO First Coincidence Run
AURIGA AU1 run: Dec 24 2003 – Jan 14 2004
LIGO S3 run: Oct 31 2003 – Jan 9 2004
92 hours 4-fold coincidence
175 hours 3-fold coincidence
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Sensitivity Spectra
single-sided PSD
best performanceduring the AU1 and the S3 run
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Geometry Considerations
Circular polarization: fAU fLHO
f 2 = F+2 + Fx
2 antenna pattern F = f cos(2) = angle between wave frame and earth frame
Linear polarization: <FAU()FLHO()>f 2=F+2+Fx
2 (independent)
LIGO Hanford
AURIGA
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Sky Coverage for LLO+LHO+AURIGA
assumption: 1. gravitational waves are
linearly polarized2. AURIGA sensitivity is
1/3 of the LLO/LHO sensitivities
required: 1. F() > 0.1 at LLO, LHO 2. F() > 0.3 at AURIGA
the color scale representsthe percentage ofdetectable polarizations
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Scientific Motivation for a Joint Burst Analysis
1. False alarm rate suppression
2. Increased effective observation times » i.e. combining all possible coincidences of 3 out of 4 or more
detectors
3. Increased detection confidence» waveform parameters can be estimated with at least 3 locations
and enough time resolution (Gursel-Tinto, 1989)
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General Strategy for a Trigger-based Analysis
Data quality and veto performed “at home” Exchange SINGLE DETECTOR triggers
» peak time and its error
» homogenously defined amplitude A (BW 850-950Hz and broadband) and its error
Exchange AT (minimum detectable) versus time
Blind analysis» all tuning is performed on time-shifted data before “opening the box”
Compare the measured test statistic to its background distribution» background measured on a different set of time shifts
Result interpretation» directional analysis (optimized)
» all-sky search (using Monte Carlo for source position distribution)
» Results interpreted for sine-gaussians, damped sinusoids, Lazarus waveforms for BH-BH mergers (10-20 M๏)
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Method 1: Directional Analysis
IGEC-style analysis, on a telescope of directions (see talk by Poggi)New: account for polarizations
Use consistent definition of amplitude in all detectors.
Threshold on the event amplitude at each detector, scaled by the antenna pattern for the given direction.
Require coincidence of at least 3 detectors.
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Method 2: “Eyes Wide Open”
No assumptions are made on direction or waveform.
A CorrPower search (see poster) is applied to the LIGO interferometers around the time of the AURIGA triggers.
Efficiency for classes of waveforms and source population is performed through Monte Carlo simulation, LIGO-style (see talks by Zweizig, Yakushin, Klimenko).
The accidental rate (background) is obtained with unphysical time-shifts between data streams.
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Sample Performance for Method 2
LIGO: SIMULATED white gaussian noisematching median BLRMS during the AURIGA-LIGO coincidence run
AURIGA: Monte Carlo average detection efficiency using -filter on sine-gaussians with f0=900Hz Q=9 and SNR>4 using ACTUAL DATA (no epoch veto)
PRELIMIN
ARY
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4.7x10-20/sqrt(Hz)1.5x10-20/sqrt(Hz)
AURIGAon real data
LIGOon white gaussian noise
uniform polarizationall-sky distribution over the AU1/S3 2-week period
SNR=4 threshold on AURIGA
Correlation confidence threshold on CorrPower as in the S2 analysis (>4)
Network efficiency ~ product of the two curves
Sample Performance for Method 2
LIGO and AURIGA efficiency for sine-gaussians with f0=900Hz Q=9
The LIGO curve was obtained on simulated data: a performance degradation
is expected on real data
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Summary and Outlook
A working group for the joint burst search in LIGO and AURIGA has been formed, with the purpose to:
» develop methodologies for bar/interferometer searches, to be tested on real data
» time coincidence, triggered based search on a 2-week coincidence period (Dec 24, 2003 – Jan 9, 2004)
» explore coherent methods
Simulations and methodological studies are in progress.
Planning on first event list exchange within the next two months, for a trigger-based burst analysis.