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Application of the Q Pipeline to LIGO’s fifth science run

This paper discusses the application of the Q Pipeline to analyze data from LIGO's 5th Science Run. The Q Pipeline is a multiresolution time-frequency search that projects whitened data onto an overlapping basis of sinusoidal Gaussians. The search is equivalent to a matched filter search for waveforms that are sinusoidal Gaussians after whitening.

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Application of the Q Pipeline to LIGO’s fifth science run

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  1. Application of the Q Pipeline to LIGO’s fifth science run Shourov K. Chatterji for the LIGO Scientific Collaboration 11th Gravitational Wave Data Analysis Workshop Albert Einstein Institute 2006 December 19

  2. Single detector Q Pipeline • Multiresolution time-frequency search for statistically significant excess signal energy • Projects whitened data onto an overlapping basis of sinusoidal Gaussians characterized by central time, central frequency, and Q (ratio of central frequency to bandwidth) • The template bank is constructed using a maximum mismatch approach similar to the matched filtering approach • The search is equivalent to a matched filter search for waveforms that are sinusoidal Gaussians after whitening • The reported normalized energy is measure of event significance and is simply twice the squared SNR that would be reported by a matched filter search 11th Gravitational Wave Data Analysis Workshop, 2006 December 19

  3. Collocated detector Q Pipeline • The two LIGO Hanford detectors (H1H2) can be combined to form two new detector data streams • H+: The optimal linear combination that maximizes the signal to noise ratio of potential signals. • Weighting factors are inversely proportional to power spectral density in each frequency bin • Resulting SNR is the quadrature sum of SNR in both detectors • H-: The H1 – H2 null stream, which should be consistent with noise for real gravitational-waves • Weighting factors are frequency independent • Residual signal resulting from calibration uncertainty can be handled by comparing against the null stream signal assuming uncorrelated data streams. 11th Gravitational Wave Data Analysis Workshop, 2006 December 19

  4. H1H2 examples • 1.4/1.4 solar mass inspiral hardware injection at 5 Mpc H1 H2 H+ yields 25 percentincrease in SNR H- consistent withdetector noise H+ H- 11th Gravitational Wave Data Analysis Workshop, 2006 December 19

  5. H1H2 examples • 1.4/1.4 solar mass inspiral hardware injection at 0.1 Mpc H1 H2 Residual much smallerthan original signal H+ H- Residual signal due tocalibration uncertainty 11th Gravitational Wave Data Analysis Workshop, 2006 December 19

  6. H1H2 examples • Time shifted detector glitch[note: placeholder for better glitch] H1 H2 H+ H- Significant H- contentindicates inconstistency 11th Gravitational Wave Data Analysis Workshop, 2006 December 19

  7. S5 Q Pipeline search • There are two primary components of this analysis • H1H2 double coincident search for combined excess signal energy followed by H1H2 null stream consistency test • H1H2L1 triple coincident search for time frequency coincidence between H1H2 triggers and L1 triggers • Upper limits will be determined using the loudest event statistic • The most significant ~100 events will be followed up • Scan auxiliary detector and environmental channels for statistically significant signal content in coincidence with gravitational-wave signal • Fully coherent test for consistency with a direction on the sky if data is available from a sufficient number of detectors 11th Gravitational Wave Data Analysis Workshop, 2006 December 19

  8. Summary of livetime and duty cycle H1 H1H2 90.1(60.1%) 3.3(2.2%) 5.1(3.4%) 34.4(22.9%) 55.8(37.2%) 12.7(8.5%) 10.2(6.8%) 7.1(4.7%) H2 L1 Livetime in days through April 3, 2006 Science mode duty cycle relative to start of S5 at LHO 11th Gravitational Wave Data Analysis Workshop, 2006 December 19

  9. Effect of H1H2 null stream veto Before nullstream veto No other data qualityor vetoes have beenapplied High thresholdnull stream veto Low thresholdnull stream veto Loudest time lag event after H1H2null stream vetoes 11th Gravitational Wave Data Analysis Workshop, 2006 December 19

  10. Most significant time lag H1H2 event • Only weakly inconsistent due to poorer sensitivity of H2 H1 H2 H+ H- 11th Gravitational Wave Data Analysis Workshop, 2006 December 19

  11. Effect of common environment • The collocated H1H2 analysis has the potential for an excess zero lag event rate due to common environment • Use data from LIGO’s fourth science run as a playground to study the effect of the null stream consistency test on the zero lag event rate • The zero lag distribution (red) appears consistent with non zero lag distributions (blue). • This is the distribution of H1signals that are too weak tohave been detectable in H2. 11th Gravitational Wave Data Analysis Workshop, 2006 December 19

  12. Follow up of interesting events • QScan searches for statistically significant signal content in auxiliary detector and environmental channels. 11th Gravitational Wave Data Analysis Workshop, 2006 December 19

  13. Estimated S5 H1H2 sensitivities • Estimated S5 H1H2 sensitivities to sinusoidal Gaussian injections based on non-zero time lag study • Assumes zero lag properties are similar to non-zero time lag properties • Tuning is still in progress 11th Gravitational Wave Data Analysis Workshop, 2006 December 19

  14. Fully coherent follow-up • A fully coherent follow-up to candidate events can be performed when data is available from three or more non-aligned detectors • Analagous to collocated H1H2 analysis • Produce linear combination of time-shifted detector data that maximizes the signal to noise ratio of potential signals • Produce linear combination(s) that contain no signal • Compare null streams with expected null stream based on the assumption of uncorrelated detector data • Produce consistency sky map • The greatest benefit comes from consistency testing 11th Gravitational Wave Data Analysis Workshop, 2006 December 19

  15. Example consistency sky maps Simulated gravitational-wave burst Simulated coincident glitch Phys.Rev. D74 (2006) 082005, gr-qc/0605002 11th Gravitational Wave Data Analysis Workshop, 2006 December 19

  16. Comments • The Q Pipeline provides three tools beyond single detector analysis that can significantly improve performance and increase detection confidence • Collocated H1H2 consistency tests • Analysis of auxiliary detector and environmental channel data for anomolous detector behavior • Coherent consistency tests using three or more non-aligned detectors (nearing completion) • The collocated H1H2 search is a planned first step in coherent hierarchical pipeline • Does not require H2 detection • Powerful veto • Computationally inexpensive 11th Gravitational Wave Data Analysis Workshop, 2006 December 19

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