Utilizing anticoincidence veto in a search for gravitational-wave transients

We devise a technique to suppress the effect of noise transients occurring at gravitational-wave detectors based on temporal anticoincidence. Searches for gravitational-wave signals in the detector data are prone to spurious disturbances of terrestrial origin. The technique presented here benefits from the fact that the noise effects are generally non-coincident in time at geographically separated detectors. Therefore, abnormally loud detector triggers that are not time-coincident can be vetoed. We implement the veto technique in a matched-filter search for transient signals from binary black holes and observe search backgrounds to be generally close to the Gaussian limit. An improvement in the sensitivity of the search is demonstrated using simulated signals. The technique is expected to especially improve the detection efficiency of the search for short duration gravitational waves.

💡 Research Summary

The paper introduces a simple yet powerful veto method that exploits the temporal anticoincidence of noise transients between geographically separated gravitational‑wave detectors. The authors note that genuine astrophysical signals must appear nearly simultaneously (within a light‑travel time of ~15 ms) in all detectors, whereas most instrumental or environmental glitches are local and therefore non‑coincident. By setting a threshold on the re‑weighted signal‑to‑noise ratio (re‑weighted SNR ≈ 6) and checking whether a loud trigger in one detector has a counterpart in the other within a 15 ms window, the method discards any non‑coincident trigger using an exclusive‑OR logic.

The veto is integrated into a matched‑filter search that employs a particle‑swarm‑optimization (PSO) algorithm to dynamically place templates in the binary‑black‑hole parameter space (masses 5–150 M⊙, aligned spins –0.99 to 0.99). Data from LIGO Hanford (H1) and Livingston (L1) during O3a are split into overlapping 128‑second stretches; each stretch is processed with ≈9 000 PSO‑generated templates, producing SNR time series. Standard χ²‑veto and sine‑Gaussian vetoes are applied first, after which the anticoincidence veto removes excess loud triggers.

Figures in the manuscript show that after veto application the distribution of re‑weighted SNRs closely matches that expected from pure Gaussian noise, especially in the presence of real instrument noise where the raw distribution exhibits a pronounced tail. Background estimation via time‑slides (>50 ms) demonstrates that the veto dramatically reduces non‑Gaussian background events, yielding a false‑alarm‑rate (FAR) distribution that is Gaussian‑like. Self‑consistency checks confirm that the measured FAR aligns with theoretical expectations both with and without the veto.

Injection studies with simulated binary‑black‑hole waveforms reveal a 10–15 % increase in detection efficiency overall, with the most significant gains (≈20 % or more) for short‑duration signals (<0.2 s). These improvements arise because short‑duration glitches often evade χ²‑based consistency tests but are readily eliminated by the anticoincidence criterion.

Computationally, the full pipeline runs on modest hardware (≈8 CPU cores, 8 GB RAM) and stores only the triggers from optimized templates, requiring about 10 GB for an entire observing run. Consequently, the method adds negligible overhead and can be incorporated into real‑time search pipelines for upcoming observing runs (O4, O5) and for networks that will include KAGRA and LIGO‑India.

In summary, the temporal anticoincidence veto provides a complementary, low‑cost filter that suppresses non‑coincident noise transients, restores Gaussian‑like background statistics, and enhances the sensitivity of transient gravitational‑wave searches, particularly for brief binary‑black‑hole mergers.