Gravitational Wave Antenna – Annex 1WG2: Joint operation of antennas and network data analysis

General objectives Promote the required coordination among the European operating detectors

to search for gravitational wave signals.

• ensure coordination to perform joint observations among gw collaborations• define the technical set-ups of pipelines of network data analysis• define programs of joint observations with other telescopes

(GRB, neutrino, optical)• support the dissemination of the results of the gravitational wave searches • compare results obtained by different observations

Outcomes • Recommendations for the planning of joint observations • Recommendations for the technical aspects involved in the data exchange and analysis• comparative studies on the results of observations• comparative studies on the relevance of the detectors

Gravitational Wave Antenna – Annex 1WG2: Joint operation of antennas and network data analysis

Deliverables • 1st year :

Annual report on the activity• 2nd year :

Annual report on the activity Recommendation report on

- planning of joint observations for different signal classes (burst, inspiral, quasi-periodic, stochastic)- technical proposals for the related data exchange and analysis

My view on the role of WG2 within our community• minimal: exchange of information • good: foster development of common methodologies for joint observations• optimal: active role in the actual planning/ implementation of joint observationsbeing a network activity, WG2 has very different kind of targets from STREGA:WG2 alone cannot be THE European group performing the actual data analysis

recommendations instead of scientific paperspromote common methodologies instead of producing scientific results

WG2: plan of the first 18 months

Sub-taskssemesters

1st 2nd 3rd

Set-up of working group          

Set-up of WEB site            

Setting general standards on software development and data formats

           

Comparison of detectors as for their compatibility and significance to joint observations for each target signal

           

Comparison of actual performances of data analysis methodologies for each target signal

           

Definition of data exchange protocols and data analysis pipelines for each target search

           

Preparation of proposals for joint observations            

Support to the implementation of the joint data analysis for the different classes of target signals

           

Annual Report            

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WG2 membership

• we extended the membership to additional researchers who expressed their interest in contributing actively and regularly to the WG2

• currently 19 members representing the major groups/collaborations. New memberships are possible, as long as the total number does not change much.

• time to time contributions by additional scientists are welcome and will be asked

Co-Chairs: Bangalore S. Sathyprakash*, Giovanni A. Prodi*

Members:Pia Astone*, Lucio Baggio*, Laura Brocco*, Sergio Frasca, Ik Siong Heng, Andrzej Krolak, Frederique Marion*, Benoit Mours, Alicia Sintes Olives, Antonello Ortolan, Archana Pai, Maria Alessandra Papa*, Joseph D. Romano, Alberto Vecchio, Andrea Vicerè*, Arlette de Waard, Graham Woan*

* appointed by GWA - Executive Board

WG2: general organization

• regular phone conferences (twice per month)- Kick-off telecon held on July 15th, 2004- 7 telecons up to now- EGO provided telecon facility from Sep 2004

• web-site dedicated to internal discussion and information exchangeelectronic Bulletin Board at http://jwg.tn.infn.it

• web public section to inform Network participants on current activities

• keep face to face meetings to a minimum. We plan to use a significant fraction of the available annual budget to support reciprocal visits of members.

• opportunity to have the first face to face proposed in Dec. (satellite to VESF meeting or GWDAW)

WG2: current activities

• formed 4 sub-groups to study:- search for transient signals (including bursts and inspirals)- search for quasi-periodic signals- search for stochastic background - data and software standards

These activities are starting up. First step is to make the science case for current and future earth-based network of detectors as well as discuss methodological issues.

• work in progress on the requests by WG3 to report on:1) effectiveness of a network of upgraded resonant and ITF detectors2) sources to be detected with a network of second/third generation detectors.

• discussion on the feasibility and technical goals of a first “exercise” data exchange (weeks of simulated or real h(t) data from European detectors in frame format)

• review of status of agreements for joint gw observations involving European detectors >> future comparative report and recommendations

Network effectiveness

• information on performances of single detectors. spectral sensitivities + antenna patternsduty cycle detection efficiency and sensitivity versus time (choose a reference signal)statistics of the estimated parameters of gw candidates (outliers …)

• estimate of the background of a joint observation

• interesting signal sources

1E-23

1E-22

1E-21

1E-20

1E-19

1E-18

800 850 900 950 1000

frequency [Hz]

stra

in p

ower

spe

ctra

l den

sity

[Hz-1

]

1E-23

1E-22

1E-21

1E-20

1E-19

1E-18

2800 2850 2900 2950 3000 3050 3100

frequency [Hz]

AURIGA 4K

NAUTILUS

AURIGA 0.1K

EXPLORER

MINIGRAIL UltraCryo

MINIGRAIL 4K

VIRGO

1E-23

1E-22

1E-21

1E-20

1E-19

1E-18

10 100 1000 10000

frequency [Hz]

stra

in p

ower

spe

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sity

[Hz-1

]

Shh of current generation detectors

Methodological issues

Blind vs exploratory search

a) exploratory search: experiment and analysis set-up are tuned using the actual data in order improve the compliance of the result with priors

Pro: high parameter estimation potential

Cons: controverse statistical interpretation (difficult to set up a test on the prior)

b) blind search: tuning is performed without looking at the results Pros: no statistical biases, it can be used to claim a discovery with correct false alarm frequentistic probability

Cons: statements are usually weaker and less outstanding, unless the signal is very clear

In the case of gravitational wave detection, assuming the prior that the first detection will be made just on the basis of statistical rarity, the adoption of blind searches seems mandatory.

BABAR F.C.Porter, "Statistical issues in particle physics - a view from BABAR", Proc. PHYSTAT2003, eds. L.Lyons, R.Mount and R.Reitmeyer (SLAC, CA, Sept.2003) p.186; also in SLAC-R-703 eConf C030908 as WEAT002 (http://www.slac.stanford.edu/econf/C030908/papers/WEAT002.pdf)

Methodological issues

Exploiting amplitude information

• detectors have different amplitude sensitivity, because they have different power spectral density, and because of different geometry/position/orientation

a) template search

• different sensitivity is not an issue, the same parameters of the source are estimated, with the proper calibration

b) template-less search

We need an empirical quantity which have to

• same expected value in all detectors

• known statistical distribution

Any procedure to extract this quantity is loosing signal power. This will produce a bias (which can be estimated if necessary when unfolding results toword any realistic known source) , but the important point is that the bias from different detectors be the same. Therefore, the same spectral weights will be implemented (in strain units).

Special case: restriction to a common bandwidth