Search for gravitational waves from binary inspirals in S3 and S4 LIGO data. Thomas Cokelaer on behalf of the LIGO Scientific Collaboration

5 Nov 2006 LSC Meeting, Boston 2 Introduction Plan of the paper: Overview : target sources, expected merger rates, S3 and S4 science runs, detector sensitivities, etc. Search parameters: coincidence windows, template banks, combined SNRs, etc. Results : loudest candidates background estimation. Upper limits Conclusion

5 Nov 2006 LSC Meeting, Boston 3 Overview (page 1) PB H BBH BN S >40 Mo LIGO runs : S3 and S4 The Parameter space was divided in 3 sub-searches, ordered by mass: Primordial black holes binaries (PBH), Binary Neutron Stars (BNS), and Binary Black Holes (BBH). No Gravitational Wave (GW) detection made Upper limits numbers

5 Nov 2006 LSC Meeting, Boston 4 Overview (page 1) Motivation for coalescing compact binary search. Notion of lower cut off frequency, and expected duration of typical binaries : 140 s (PBH), 25 s(BNS), 1 s(BBH). The theoretical merger rate for the 3 types of binaries

5 Nov 2006 LSC Meeting, Boston 5 Overview (page 1) Introduce the LIGO detectors naming convention. Introduce the S3 and S4 run : durations. Introduce the notion of horizon distance.

5 Nov 2006 LSC Meeting, Boston 6 Overview (page 2) Examples of typical horizon distance expectd during the runs (using the specific lower cut-off frequencies used in each search) : ~6Mpc, 16, 77 Mpc in PBH, BNS and BBH, respectively. Plan, organisation of the paper : II search parameters, pipeline issues. III Results of the searches IV Upper limits Conclusion

5 Nov 2006 LSC Meeting, Boston 7 Data analysis pipeline (page 2) This table gives the times analysed when at least two detectors were operating in science mode. Coincident data and times analysed. Notion of Playground data (9% of the full data set.) Veto issues : time vetoed in S3 (5% of H1/H2, 10% of L1) and S4 (10% of H1H2).

5 Nov 2006 LSC Meeting, Boston 8 Matched filtering is used for the detection. Definition of the effective distance (physical distance / a value function of the detector response functions) Inspiral search parameters. Individual masses in [0.35 – 1]Mo for PBH binaries [1 – 3] Mo for BNS [3 – 40] for BBH in S3 [3 - 80] for BBH in S4 Total mass constraint to 40 and 80 solar mass in S3 and S4, respectively. The values of the lower cut-off frequencies in each search and two runs varies. Data analysis pipeline (page 3)

5 Nov 2006 LSC Meeting, Boston 9 Template bank notion: minimal match used, template bank sizes. Two different filtering methods were used depending on the search : SPA for PBH binaries and BNS, Phenomenological for BBH. Threshold used at the single detector analysis: 6.5 in BNS and PBH. 6 in BBH. Clustering of 16 over each single template. 10 ms over the bank. Data analysis pipeline (page 3)

5 Nov 2006 LSC Meeting, Boston 10 PBH and BNS searches : effective SNR which takes the chis-square into account: Data analysis pipeline (page 3)

5 Nov 2006 LSC Meeting, Boston 11 BNS and PBH searches: interest of the chi-square, consequence on the two coincidence steps and Combined SNR. Define chirp mass and eta. Introduce coincidence window between detectors. BBH search : no chi-square. Combined SNR. Coincidence window. Coincidence windows in the 3 searches. Data analysis pipeline (page 4)

5 Nov 2006 LSC Meeting, Boston 12 Background definition : 100 experiments with time- shifts of 10 s in H2 and 5 s in L1. Interest of the effective SNR described in Figure 2. Distribution of the triggers in effective SNR and effective distance plots. (next slide) Perform software injections. Efficiencies of the detection process. Tune the search parameters so as to increase efficiencies and decrease background loudest triggers. Data analysis pipeline (page 4) We compare in-time coincident triggers with the background triggers, function of combined SNR. Look at loudest candidates.

5 Nov 2006 LSC Meeting, Boston 13 Data analysis pipeline (page 5)

5 Nov 2006 LSC Meeting, Boston 14 BNS : no triple coincident triggers (neither in- times nor in time-shifts). Loudest candidate in H1L1 coincidence. Loudest candidate and Background (page 5) Similar results for PBH: no triple. Loudest candidate in H1L1 coincidence. Introduction on loudest candidates and background estimate. P_B(rho_c) = probability that all background events have combined SNR less than rho_c: low P_B -> plausible GW event. High P_B -> background event.

5 Nov 2006 LSC Meeting, Boston 15 BBH: triple coincident triggers present in S3 and S4. Double coincidences in excess in H1H2. Loudest non-playground candidate has rho_c = 22.2 Loudest candidate and Background (page 6) No plausible GW from inspiral compact binaries.

5 Nov 2006 LSC Meeting, Boston 16 Loudest candidate and Background (page 6) Loudest candidates

5 Nov 2006 LSC Meeting, Boston 17 Upper limits (page 6) No plausible candidates, so we derived the upper limits based on the most sensitive run : S4. We use only non-playground data. Calculations based on the loudest event statistic, which uses both the detection efficiency at combined SNR of the loudest candidate and the associated background probability.

5 Nov 2006 LSC Meeting, Boston 18 Upper limits (page 7) Details on the loudest candidates in each search and type of coincidences. Bayesian upper limits, assuming uniform prior needs: C_L, cumulative blue luminosity we are sensitive to at the loudest combined SNR. T, observation time P_B -> likelihood that the loudest candidate is due to foreground C_L needs (1) efficiencies at loudest event and (2) catalog of galaxies.

5 Nov 2006 LSC Meeting, Boston 19 Upper limits (page 8) Systematic errors: calibration inaccuracies, finite number of Monte Carlo simulations, mismatch between true GW and template family, etc. PBH = 4.9 /yr/L_10 BNS = 1.5/yr/L_10 BBH = 0/7/tr/L_10

5 Nov 2006 LSC Meeting, Boston 20 Upper limits (page 9)

5 Nov 2006 LSC Meeting, Boston 21 Conclusion (page 8) No GW detection BBH search suffered from high combined SNR triggers both at single and coincidence step. The BNS and PBH searches have significantly reduced the background rate (effective SNR effect, in particular) New Upper limits Future : switch to physical template families for the BBH search. Use the same pipeline as in S3/S4 for future searches.

5 Nov 2006 LSC Meeting, Boston 22 References (page 9) Several companion papers entering in the detail of the analysis are in preparation: galaxy catalog systematic errors in U.L calculation tuning veto pipeline etc.

5 Nov 2006 LSC Meeting, Boston 23 Questions ?