Silvia Poggi - GW burst detection strategy in non-homogeneus Silvia Poggi - GW burst detection strategy in non-homogeneus networks networks Detection strategies for bursts in networks of non-homogeneus gravitational waves detectors Silvia Poggi * , Lucio Baggio*, Giovanni A.Prodi*, Alessandro Mion*, Francesco Salemi § * University of Trento & INFN § University of Ferrara & INFN The time coincidence strategy adopted by the International Gravitational Event Collaboration (IGEC) was suited for a network of almost equal and parallel detectors, and assuming a template. (P. Astone et al., Phys Rev D 68 022001 (2003) ) Considerations on the directional sensitivity and sky coverage in bar/interferometer network analysis: • if gw’s are linearly polarized • If gw’s are circularly polarized Characteristics of the cross-correlation search (coherent coincidence analysis) Extension of the classical IGEC analysis (incoherent coincidence analysis) Outline : Comparison between coherent and incoherent methods
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Silvia Poggi - GW burst detection strategy in non-homogeneus networks Detection strategies for bursts in networks of non-homogeneus gravitational waves.
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Silvia Poggi - GW burst detection strategy in non-homogeneus networksSilvia Poggi - GW burst detection strategy in non-homogeneus networks
Detection strategies for bursts in networks of non-homogeneus gravitational waves detectors
Silvia Poggi*, Lucio Baggio*, Giovanni A.Prodi*, Alessandro Mion*, Francesco
Salemi§
* University of Trento & INFN§ University of Ferrara & INFN
The time coincidence strategy adopted by the International Gravitational Event Collaboration (IGEC) was suited for a network of almost equal and parallel detectors, and assuming a template. (P. Astone et al., Phys Rev D 68 022001 (2003) )
Considerations on the directional sensitivity and sky coverage in bar/interferometer network analysis:
• if gw’s are linearly polarized• If gw’s are circularly polarized
Characteristics of the cross-correlation search (coherent coincidence analysis)
Extension of the classical IGEC analysis (incoherent coincidence analysis)
Outline:
Comparison between coherent and incoherent methods
Silvia Poggi - GW burst detection strategy in non-homogeneus networksSilvia Poggi - GW burst detection strategy in non-homogeneus networks
In order to reconstruct the wave amplitude h, any amplitude has to be divided by
Introduction
At any given time, the antenna pattern is:
it is a sinusoidal function of polarization , i.e. any gravitational wave detector is a linear polarizer it depends on declination and right ascension through the magnitude A and the phase )),(2cos(),(),,( AF
),,( F
We will characterize the directional sensitivity of a detector pair by the product of their antenna patterns F1 and F2
F1F2 is inversely proportional to the square of wave amplitude h2 in a cross-correlation search
F1F2 is an “extension” of the “AND” logic of IGEC 2-fold coincidence
This has been extensively used by IGEC: first step is a data selection obtained by putting a threshold F-1 on each detector
Silvia Poggi - GW burst detection strategy in non-homogeneus networksSilvia Poggi - GW burst detection strategy in non-homogeneus networks
Classical “IGEC style” coincidence search
detector 1
detector 2
detector 2
AND
AND
AND
detector 3
Detectors: PARALLEL, BARS Shh: SIMILAR FREQUENCY RANGE Search: NON DIRECTIONAL Template: BURST = (t)
The search coincidence is performed in a subset of the data such that: the efficiency is at least 50% above the threshold (HS) significant false alarm reduction is accomplished
The number of detectors in coincidence considered is self-adapting
Silvia Poggi - GW burst detection strategy in non-homogeneus networksSilvia Poggi - GW burst detection strategy in non-homogeneus networks
Probability of detection in “IGEC style” coincidence with different antenna patterns
HS = 10 HTHS= 5 HT
51.3 %
22.9 %
In IGEC style non-directional search, the probability of detection of a linearly polarized signal with random polarization is a function of source direction.
The relative amplitude sensitivity of detectors greatly affects the sky coverage of a network search.
Case of LHO – AURIGA assuming AURIGA is 3 times less sensitive. Probability of detection of the non-directional “IGEC style” search.
Threshold of AURIGA HAURIGA= 3 HT Threshold of LHO HLHO= HT
Polarization averagePolarization and time average Sky average
Silvia Poggi - GW burst detection strategy in non-homogeneus networksSilvia Poggi - GW burst detection strategy in non-homogeneus networks
Naïve cross-correlation search
Detectors: PARALLEL Shh: SAME FREQUENCY RANGE NEEDED Search: NON DIRECTIONAL Template: NO
Selection based on data quality can be implemented before cross-correlating.
The efficiency is to be determined a posteriori using Montecarlo.
The information which is usually included in cross-correlation takes into account statistical properties of the data streams but not geometrical ones, as those related to antenna patterns.
Silvia Poggi - GW burst detection strategy in non-homogeneus networksSilvia Poggi - GW burst detection strategy in non-homogeneus networks
HS2 = 100 THS
2 = 25 T
75.6 %
45.6 %
20.6 %
Probability of detection in cross-correlation strategy
REMARK: the efficiency is not taking into account the contribution of the noise therefore the result of the cross-correlation at threshold T is not directly comparable with that of IGEC at HT=T1/2
Case of LHO – AURIGA assuming AURIGA is 3 times less sensitive. Probability of detection of the cross-correlation search
Signal2 > TT =HAURIGA x HLIGO
Polarization averagePolarization and time average Sky averageHS
Silvia Poggi - GW burst detection strategy in non-homogeneus networksSilvia Poggi - GW burst detection strategy in non-homogeneus networks
Comparison between “IGEC style” and cross-correlation
IGEC style search was designed for template searches. The template guarantees that it is possible to have consistent estimators of signal amplitude and arrival time. A bank of templates may be required to cover different class of signals. Anyway in burst search we don’t know how well the template fits the signalA template-less IGEC search can be easily implemented in case of detectors with equal detector bandwidth. In fact it is possible to define a consistent amplitude estimator. (Karhunen-Loeve, power…)
Cross-correlation among identical detectors is the most used method to cope with lack of templates.
Cross-correlation in general is not efficient with non-overlapping frequency bandwidths, even for wide band signals.
We are working to the extension of IGEC in case of template-less search among different detectors. It is needed to determine spectral weights common to all detectors, setting a balance between efficiency loss and network gain (sky coverage and false alarm rate)