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GEO outlook

Benno Willke (presented by Bernard Schutz)

LSC meeting, MIT Nov 2006

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GEO in S5

Jan – May: overnight and weekend mode 1255 hours (52 days) of calibrated data

May-Oct: 24/7 mode (141 days)

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Sensitivity comparison (including Virgo)

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LHO 4k June '06LLO 4k June '06LHO 2k June '06Virgo Sept '06S5 N&W Mar 23 `06S5 Sept. '06

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strategic decision - options

continue to run GEO600 in co-incidence with L1/H1/H2 (Virgo) in S5

run GEO600 during Enhanced LIGO commissioning break (late 2007 – early 2009) in co-incidence with H2 (and Virgo) improve GEO sensitivity to match H2 over an as

large as possible frequency range make necessary infrastructure an detector changes

before start of L1 downtime to achieve high duty factor

start GEO-HF upgrades after S5

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strategic decision – input

strong LSC involvement asked data groups how useful GEO in its current sensitivity is

during S5 discussed options in LSC operations committee asked LIGO directorate for advice

commissioning team was charged to analyze how GEO could be improved and what “maintenance” work was required to prepare GEO for a long science run in 2008 possible benefit risk resources required how useful is this for GEO-HF ?

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search groups assessment

LSC search groups' answers to the questions:

● how useful is GEO data now ?

● would it be better if GEO went off the air and its sensitivity were improved ?

● how much would GEO's sensitivity have to be improved to make an impact ?

LSC search groups' answers to the questions, in short:

● how useful is GEO data now ? not enough to be routinely analyzed

● would it be better if GEO went off the air and its sensitivity were improved ? Yes

● how much would GEO's sensitivity have to be improved to make an impact ? ~H2

more detailed reports are available

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GEO600 – future

as GEO in it’s current sensitivity does not contribute much to the S5 data analysis

we allow shorter and longer commissioning breaks and operate the detector in science mode in between (main goal is to help with parameter estimation in case of a GW signal)

we support the proposal made by the commissioning group which should lead to a new decision point in March could excess noise 200-500Hz and above 500Hz be found and

reduced what are the prospects of further improvements in the sensitivity how close are we to H2 can LIGO commit to run H2 in coincidence with GEO in 2008

main goal of commissioning: to take data in 2008 we do not define a sensitivity goal / best effort

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we do not produce veto lists for S5 but follow the required steps to have the veto pipelines available if required

we should try to better understand the low frequency glitches and reduce them

when enhanced detectors are in science mode we take GEO down for conversion into a high frequency detector GEO-HF

this work has highest priority in the GEO collaboration

commissioning team works full time on this

Stochastic:The stochastic group does not use GEO data in any of its analyses, wouldn't be able to make profitable use of it until the low frequency(in the 150-200 Hz region or lower) strain sensitivity of GEO becameclose to that of H2.

Inspiral:

S5 LIGO BNS inspiral range up to Feb6th

GEO inspiral ranges in Sept 06

Inspiral:

S5 LIGO BBH inspiral range up to Feb6th

Inspiral:

GEO data has not been actively searched, but kept for possible follow-up of a loud event. However: a candidate event at threshold in GEO would correspond to an SNR of about 40 in either L1 or H1. Hence the increase in detection confidence would be negligeable. The inspiral group thinks that GEO should sacrifice some science time and take (short) commissioning breaks to further improve the sensitivity. This will mostly impact BNS searches.

Bursts, generalities:

● The GEO 600 detector can potentially make contributions to severalaspects of the burst search.

● The LIGO-GEO S4 coherent Waveburst analysisshowed that GEO can be folded into the LSC network without greatlyreducing the sensitivity of the analysis...

● GEO can also contribute to triggered burst searches: since GEO 600 is not aligned with the LIGO, it can contribute to searches where the trigger occurs at an unfavourable sky location for the LIGO detectors. Moreover, the high duty cycle of GEO 600 (~90%) increases the coverage of the LSC detector network.

● For a burst gravitational wave search, both the sensitivity and glitch rate of the detector are important.

Bursts, some details:●Preliminary investigations using coherent Waveburst on LIGO and GEO data acquired on the first 16 days of June 2006 have shown a reduction in the glitch rate for the same frequency range used in the S4 analysis. However, there is still an excess number of glitches above 768 Hz which can probably attributed to GEO. Glitches in GEO between 1800 and 2000 Hz have been observed by the GEO experimentalists using the HACR pipeline (which is used to monitor the glitch rate in GEO). The glitches were identified and fixed around the 22nd of June, 2006. ● A preliminary GRB analysis was also performed using LIGO and GEO S5 data for GRBs observed between June and September 2006. Of 32 GRB triggers that occurred in this period, 3 occurred when there was data from only one LIGO detector and GEO. There was a slight excess observed in the cross-correlation distribution. It is unclear, at the stage, whether this excess is caused by glitches in GEO data. ● The coherent Xpipeline was applied to data around GRB060813. This particular GRB was chosen because it was at a time and position that was favourable for GEO. A dry run of the pipeline was performed to examine the noise characteristics and no actual on-source data was used. It was determined, by software injections, that GEO contributes ~15% in amplitude (2% in power) to the likelihood for frequencies above 700 Hz and rapidly reduces to 0% for frequencies below 700 Hz.

Bursts, recommendation:

the Burst group supports the proposal for a 2-month shutdown of GEO600 for a general upgrade. In particular, the Burst group would like commissioning work to concentrate on bringing the high-frequency noise baseline down to match LIGO and target a reduced glitch rate.

CW, targeted searches :

For searches targeted at known pulsars the current sensitivity levelof GEO relative to LIGO (October 2006) means it does not contributesignificantly to our overall sensitivity. For these searches itwould appear better for GEO to be off the air for a while andattempt a sensitivity improvement if, after that improvement, GEOhad a comparable sensitivity to H2 for at least one target pulsar(note that the relative contributions of the interferometers scaleas the inverse of their power spectral densities at the signalfrequency).

CW, wide area searches :

● the bottom line is very similar to what outlined for targeted searches of known objects.

● However since the putative source is a-priori unknown we are notbound by any spindown-inferred upper limit and can imagine a "lucky"(in the sense of statistically improbable) nearby, highly deformedcompact object whose detection may be *confirmed* by a long coherenttargeted search over GEO data.

● If this follow-up search could be truly just a single-template search, GEO could confirm the detection with an h0 sensitivity five times higher than that of a hierarchical search with about 3 months of data, if its sensitivity were the same as LIGO's. If it were a factor of 2 worse then 6 months of data would be needed. However, it is unlikely that such a follow-up could be a single template search, hence computational cost evaluations would, in fact, limit the integration time that a coherent follow-up could cover.

● The conclusion, is, in this case too that a real contribution from GEO data could come if its sensitivity was within a 20%-25% of the LIGO detectors (i.e. very close to H2).

If that were the case we could also envision using GEO data to search in those bands were known noise artifacts severely limit LIGO's performance, for example the 60Hz harmonics.

...a final comment :

some of the experimeters in our search groups have reminded us that we are asking of a 600m baseline IFO to reach the same sensitivity as a 2km one. If this can be accomplished it's worthwhile in itself, apart from any science that can then be done with that data.

Else the recommendation is quite clear:

to be useful for astrophysical searches, GEO's got to match H2 sensitivity in some frequency band.