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Reducing False Alarms in Searches for Gravitational Reducing False Alarms in Searches for Gravitational Waves from Coalescing Binary SystemsWaves from Coalescing Binary Systems
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Andrés C. RodríguezLouisiana State University
M.S. Thesis Defense Thesis Advisor: Professor Gabriela González
6.20.07LIGO-G070394-00-Z
• LIGO
• Sources of Gravitational Waves
• Data Analysis for Coalescing Binary Systems
• Methods to Reduce False Alarms - 2 Veto, r2 Test
• LIGO S3 Primordial Black Hole Search
• Conclusions
OutlineOutline
6.20.07 02
Laser Interferometer Gravitational Wave Observatory (LIGO)Laser Interferometer Gravitational Wave Observatory (LIGO)
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s(t) = [Lx - Ly]/L
6.20.07 03
LIGO SitesLIGO Siteslsc.orglsc.org
Hanford: two interferometers in same vacuum envelope - 4km (H1), 2km(H2)
Livingston: 4km (L1)
Generated with Google EarthTM6.20.07 04
Improved Sensitivity, Improved Sensitivity, LIGO Science RunsLIGO Science Runs
6.20.07 06
• S1 Aug ‘02 - Sept ‘02
• S2 Feb ‘03 - April ‘03
• S3 Oct ‘03 - Jan ‘04
• S4 Feb ‘05 - March ’05
• S5 Nov ‘05 - current
7/9/2003 `LIGO Scientific Collaboration - Amaldi 2003
Sources of Gravitational WavesSources of Gravitational Waves
• periodic signals: pulsars
• burst signals: supernovae, gamma ray bursts
• stochastic background: early universe, unresolved sources
• compact binary coalescing (CBC) systems: neutron stars, black holes
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6.20.07 05
Crab pulsar (NASA, Chandra Observatory)
NASA, WMAP
6.20.07 07
• General Relativity predicts the decay of the binary orbit due to the emission of gravitational radiation.
• Waveforms can be well approximated by 2nd order post-Newtonian expansion.
Non -spinning waveforms parameterized by: » masses: m1,m2, total mass M, or reduced mass » orbital phase & orientation » position in the sky: ,
Coalescing Binary SystemsCoalescing Binary Systems
• Effective Distance:
• Chirp Mass:
• Symmetric Mass ratio :
6.20.07 08
Coalescing Binary Systems IICoalescing Binary Systems II
Matched Filtering Matched Filtering
6.20.07 09
*
• Data stream searched using matched filtering between data & template waveform:
Effective Distance:
• Matched Filter:
• Characteristic Amplitude:
• Signal to Noise Ratio (SNR):
• Inspiral Trigger: &
• Data Collection
• Template Bank Generation: h(f)
• Matched Filter I: z(t), (t), ask > *
• 1st Coincidence (time, , Mc )
• Matched Filter 2: 2, r2 Test
• 2nd Coincidence (time, , Mc)
• Follow Up
Inspiral Inspiral Coincidence Coincidence
PipelinePipeline
*
,
Inspiral Trigger:
&
Methods to Reduce False Alarms I:Methods to Reduce False Alarms I:22 Veto Veto
6.20.07
*2
Simulated Waveform vs False AlarmSimulated Waveform vs False Alarm
6.20.07 12
Methods to Reduce False Alarms II:Methods to Reduce False Alarms II:rr22 Test Test
6.20.07
• Use the r2 time series (2/p) as a method to search for excess noise.• Impose a higher r2 threshold (r*2) than the search employs.
» Count the number of time samples (t) above r*2 in a time interval (t*) before inferred coalescence
t = 0.9 sec
t*
r*2
*2
Methods to Reduce False Alarms IIMethods to Reduce False Alarms IIrr2 2 Test Result: S4 BNS SearchTest Result: S4 BNS Search
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Simulated Waveforms: 0% falsely dismissedFalse Alarms: 35%, 36% vetoed
rd r
t = 0.26 sec
rr22 Test Results: Test Results: Searches performed by CBC Group in the LSCSearches performed by CBC Group in the LSC
6.20.07 15
• r2 test is included in current LIGO searches: S5 Low Mass (M < 35MSOL) 1 year
• Black hole composed with mass < 1.0 MSOL is believed to be a primordial black hole (PBH).
• They are compact objects may have formed in the early, highly compressed stages of the universe immediately following the big bang.
• Speculated to be part of the galactic halo or constituent of dark matter (small fraction).
• Binary system composed of two PBH’s will emit gravitational waves that may be detectable by LIGO.
• A PBH binary composed of 2 x 0.35 MSOL objects would have a coalescence frequency of 2023Hz and would spend about 22 seconds in LIGO’s sensitive band.
S3 Primordial Black Hole (PBH) Search IS3 Primordial Black Hole (PBH) Search I
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• Target Sources:
S3: October 3 - January 09: 2004
* Numbers in () represent time left after data used for tuning search.
S3 PBH Search IIS3 PBH Search II
• Coincidence Windows
• H1H2 Effective Distance Cut
, = 0.45
• Parameters Selected:
S3 PBH Search III - TuningS3 PBH Search III - Tuning
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• Effective SNR:
• Combined SNR:
S3 PBH Search IV - TuningS3 PBH Search IV - Tuning
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S3 PBH Search V: ResultS3 PBH Search V: Result
6.20.07 20
• No triple coincident foreground candidate events or background events were found.• Number of double coincidences found ( ) consistent with measured background (+).
c2
• r2 test greatly reduces rate of false alarms in LIGO CBC searches.
• The r2 test be incorporated into future LIGO searches: S5 Low Mass (M < 35MSOL) 1 year.
• A search for primordial black hole binary systems (M < 1MSOL) in LIGO’s S3 run was performed with results consistent with measured background.
ConclusionsConclusions
6.20.07 21
Prof. Gabriela González
Thesis Committee: Prof. James Matthews, Prof. David Young, Prof. Jorge Pullin
LSU-LIGO Group: Chad, Ravi, Rupal, Prof. Warren Johnson, Jake, Dr. Myungkee Sung, Prof. Joseph Giaime, Shyang, Andy W., Jeff, Dr. Romain Gouaty
CBC Group: Dr. Duncan Brown, Dr. Stephen Fairhurst, Dr. Eirini Messaritaki, Prof. Patrick Brady, Dr. Alexander Dietz, Drew Keppel
LSC: Prof. Peter Shawhan, Prof. Alan Weinstein, Prof. Laura Cadonati, Dr. John Whelan, Prof. Vicky Kalogera, Dr. Bill Kells
LSC and CBC Group for access to LIGO data
LSU Dept. of Physics & Astronomy, NSF, Alfred P. Sloan Foundation
This research has been supported by National Science Foundation grants: PHY-0135389, PHY-0355289.
Thank You!Thank You!
Extra SlidesExtra Slides
BNS WaveformBNS Waveform
PBH WaveformPBH Waveform
BBH WaveformBBH Waveform
SNRSNR
\xi^2\xi^2
InjectionInjection
Injection vs TriggerInjection vs Trigger
r^2 testr^2 test
r^2 exampler^2 example
r^2 - S3 BNSr^2 - S3 BNS
r^2 - S3 PBHr^2 - S3 PBH
r^2 - S4 BNSr^2 - S4 BNS
r^2 - S4 PBHr^2 - S4 PBH
r^2 - S5 BBH epoch 1r^2 - S5 BBH epoch 1
PipelinePipeline
S3 PBH - Effective Distance CutS3 PBH - Effective Distance Cut
Effective SNR - S3 PBHEffective SNR - S3 PBH
Tuning - S3PBHTuning - S3PBH