LIGO Data Analysis: Status and Plans

1
LIGO Data Analysis Status and Plans

• Patrick Brady
• University of Wisconsin-Milwaukee
• LIGO Scientific Collaboration

2
Outline of talk

• First LIGO science data run (S1)
• Summary of run
• Organization of LIGO data analysis efforts
• Status of each effort
• Detailed discussion of burst/inspiral analysis
• Emphasis because of TAMA/LIGO coincidence
  analysis
• Plans for second LIGO science data run (S2)
• Online analysis plans/status
• Tools used in control room
• Summary

3
LIGO Run Schedule

• Science runs are interspersed with engineering
  runs and commissioning activities

strain noise per root Hz
Jul
Oct
Jul
Oct
Jun
Sep
Jun
Sep
Feb
Mar
Apr
Aug
Nov
Feb
Dec
Mar
Apr
Aug
Nov
May
May
Jan 2002
Jan 2003
E10,
S3

• E7

• E8

S2

• S1

• E9

Now
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LIGO sensitivity at start of S1

• S1 run
• 23 Aug 9 Sep, 2002
• Standard candle
• 2 x 1.4 Msun optimally oriented binary
• S1 reach includes
• Milky Way
• LMC
• SMC

5
Data from S1 run
H1 235 Hours
H2 298 Hours
L1 170 Hours
3x 95.7 Hours

• S1 total run time 408 hours 17 days
• H1 (4km, Hanford) duty cycle 57.6
• H2 (2km, Hanford) duty cycle 73.1
• L1 (4km, Livingston) duty cycle 41.7
• Triple coincidence duty cycle 23.4

Green bands with black borders indicate locked
segments
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Data analysis groups

• Burst and other transients
• Sam Finn and Peter Saulson (co-chairs)
• http//www.ligo.caltech.edu/ajw/bursts/bursts.htm
  l
• Continuous Wave
• Michael Landry and Mariallessandra Papa
  (co-chairs)
• http//www.lsc-group.phys.uwm.edu/pulgroup/
• Inspiral
• Patrick Brady and Gabriel Gonzalez (co-chairs)
• http//www.lsc-group.phys.uwm.edu/iulgroup/
• Stochastic
• Peter Fritschel and Joe Romano (co-chairs)
• http//feynman.utb.edu/joe/research/stochastic/up
  perlimits

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Burst Group Activities

• Search for bursts of unknown origin/waveform
• Generate event triggers using SLOPE, TFCLUSTERS,
  POWER
• Veto triggers due to instrumental artifacts
• Determine upper limit on rate as function of
  strain
• Monte Carlo by simulated injections of
  astrophysical motivated signals (Zwerger et al)
  and other burst waveforms
• Search for bursts associated with GRBs.
• Triggered analysis of on-source times
• Result by comparison of on-source versus
  off-source distributions
• First EM triggered search with LIGO

8
Continuous Wave Group Analysis

• Known pulsar searches
• Catalog of known pulsars
• Heterodyne narrow BW folding data
• Coherent frequency domain search using Hough
  transform
• All sky unbiased
• Sum short power spectra (no doppler correction)
• Wide area search
• Hierarchical Hough transform code is under
  development
• Demodulation is functioning and used in known
  pulsar search
• Demodulation points on sky under control
• Efficient positioning of spindown/sky points
  under development

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Inspiral Group Activities

• Binary Neutron Star Search
• Bread n butter source for LIGO
• Determined upper limit on the rate of BNS
  inspirals in the universe
• Black hole MACHO binary search (0.5ltm1,m2lt1.0)
• Speculative source
• MACHO search will use same pipeline as BNS
• Unbiased search and upper limit will follow
  neutron star result
• Binary black hole search (m1,m2 gt 3.0 Msun)
• An unbiased search will not be made due to
  proximity of S2
• Will use the full S1 data set to explore
  techniques for S2
• Need to better understand veto strategies for BBH

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Stochastic Group Activities

• Analytic calculation of expected upper limits
  (100 hrs)
• W for LHO 2k-LHO 4k will provide the most
  stringent direct observational upper limit to
  date
• Coherence measurements of GW channels show little
  coherence for LLO-LHO 2k correlations
• Investigation of effect of line removal for LHO
  2km-LHO 4km correlations (e.g., reduction in
  instrumental correlated noise)
• Injection of simulated stochastic signals into
  the data and extraction from the noise to
  validate end-to-end capability of analysis
• Correlations between LLO with ALLEGRO bar
  detector
• ALLEGRO was rotated into 3 different positions
  during earlier E7 run
• Analysis in progress

11
Playground Data Set

• Representative sample of data distributed over
  run
• Not used in determining astrophysical results
• Used to tune thresholds
• Determine veto cuts
• Gain experience without introducing bias into
  upper limit analyses
• Characteristics
• 9 hours of triple coincident data was selected
  for this purpose
• Chosen by Gabriela Gonzalez in consultation with
  others on site
• Representative of broad range of instrumental
  behavior
• Which groups used it?
• Inspiral group
• Burst group
• Stochastic group

12
Burst Trigger Generation

• One hour summary plot
• Confidence
• Log( probability that trigger is caused by
  Gaussian noise)
• Large negative value is loud burst
• Time-frequency plot
• Green 0 gt confidence gt -100
• Red confidence lt -100
• No. of events
• Triggers per 10 seconds
• Event definition
• Different for TFCLUSTER, SLOPE, POWER

Trigger in 200-400Hz band with duration 100 sec
13
Inspiral Trigger Generation Templates

• Use template based matched filtering algorithm
• Template waveforms for non-spinning binaries
• 2.0 post-Newtonian approx.
• Computational efficiency
• Stationary phase approximation to Fourier
  Transform
• Discrete set of templates labeled by M1, M2
• 1.0 Msun lt m1, m2 lt 3.0 Msun
• 2110 templates
• At most 3 loss in SNR

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Inspiral Trigger Generation

• AS_Q processed in chunks of 256 seconds
  down-sampled to 4096Hz
• Each chunk is divided into 7 segments of 64
  seconds overlapped by 32 seconds
• For each template
• Compute the SNR large values indicate that GW
  channel correlates well with the template
• If SNR gt 6.5, compute a2 small values
  indicate that SNR was accumulated in a manner
  consistent with an inspiral signal.
• If a2 lt 5.0, record trigger
• Triggers are clustered within duration of each
  template, but multiple templates can trigger at
  same time.

15
Dealing with Non-Gaussian Spurions

• Example at LIGO Louisianna
• Cattle Guard
• (Gonzalez, Chickarmane, Saulson during E7)
• How to deal with them?
• Auxiliary channels vetoes
• Can physical cause be tracked?
• Use PEM other channels
• Potential vetoes
• Evaluated vetoes generated by several tools

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Veto Investigations

• Tuned veto SNR thresholds and windows using the
  playground data focused on eliminating the
  highest-SNR candidates without introducing much
  deadtime
• Best channels turned out to be auxilliary
  interferometer channels
• Example from inspiral analysis (similar for
  burst)
• Livingston 4km Net deadtime 2.8
• Hanford 4km Net deadtime 0.3
• Hanford 2km Net deadtime 3.2
• Must check that veto conditions would not veto a
  real gravitational wave!
• Studied coupling using hardware injections in
  differential control end mass excitations
• Found some surprise couplings which may involve
  abandoning certain vetoes

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Effectiveness of Vetoesfor S1 Playground Data
So, how do triggers vetoes fit together in
analysis pipeline?
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GW Injections
Auxiliary Channels
Matched Filter
Filter
Triggers
Veto Triggers
-
H1 clean Not L1
L1 clean Not H1
L1 H1 clean
H1 Sees?
Yes
No
No
Coincidence?
Dump
Yes
Event Candidates
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Sample Population Monte Carlo

• Binary Neutron star population
• Mass distribution derived from population
  synthesis models
• Spatial distribution out to 200kpc including
  Milky Way, LMC and SMC
• LMC and SMC contribute about 12 of a Milky Way
  equivalent Galaxy
• Signals injected into data stream and used to
  determine efficiency of pipeline to detection of
  BNS population

20
Testing with Hardware Injection
Inspiral Injections into hardware
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Testing with Hardware Injections

• Pre-run 2 x 1.4 Msun into L1LSC-DARM_CTRL-EXC

Pre-run 2 x 1.4 Msun into L1LSC-ETMX-EXC
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LIGO First Science Run Synopsis

• Compact object inspiraling waveforms
• BNS coverage will include the Milky Way, plus
  LMC, SMC
• Black hole MACHO search under way
• Bursts/transient events
• 96 hours of 3X coincidence
• 2 different (complementary) filters applied to
  data
• frequency-time clustering algorithm, time-domain
  slope detector
• Efficiency using astrophysically motivated SNe
  waveforms and other.
• Continuous wave sources
• Initial searches target known EM sources, e.g.
• - PSR J19392134 (P 1.557 ms, search and
  analysis in progress)
• Sco X-1 (in progress - 500 Hz - 600 Hz,
  multi-parameter search)
• Stochastic background
• Limiting sensitivity for W will be better than
  previous direct GW observational determinations
  with resonant bars (narrowband)

23
Plans for S2

• S2 14 Feb 14 April 2003
• Working groups
• have well defined primary analysis path for S2
  data
• Plan to extend/enhance methodology from S1
• Some new tools are under development, e.g
  coherent multi-detector analysis
• Veto development will be a major focus of the S2
  detector characterization effort
• Desire to understand the instrumental origin of
  glitches
• Significant effort has been put into hardware
  injection plan
• Daily hardware injections of astrophysical
  signals to help calibrate systematics

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Plans for S2

• Trigger generators to run in real-time
• Burst searches TFCLUSTERS, POWER, SLOPE
• Inspiral searches
• Known pulsar demodulation
• External trigger searches
• Issues that caused problems in S1 but have been
  fixed
• Accurate, real-time calibration data available
• On-line monitoring tool to provide alarms to
  control room

25
Conclusion

• LIGO Scientific Operation
• Started in Aug. 2002!
• Analysis has been proceeding
• First results should be announced in Mar 2003
• Second run scheduled 14 Feb - 15 Apr 2003
• Sensitivity should be almost 10x better than S1
• Moving towards real-time analysis environment
• Looking forward to the TAMA/LIGO coincidence
  effort