E. Hirose

A hierarchical method for vetoing noise transients in gravitational-wave detectors

Non-Gaussian noise transients in interferometric gravitational-wave detectors increase the background in searches for short-duration and un-modeled signals. We describe a method for vetoing noise transients by ranking the statistical relationship between triggers in auxiliary channels that have negligible sensitivity to gravitational waves and putative gravitational-wave triggers in the detector output. The novelty of the algorithm lies in its hierarchical approach, which leads to a minimal set of veto conditions with high performance and low deadtime. After a given channel has been selected it is used to veto triggers from the detector output; then, the algorithm selects a new channel that performs well on the remaining triggers and the process is repeated. This method has been demonstrated to reduce the background in searches for transient gravitational waves by the LIGO and Virgo collaborations.

Angular instability due to radiation pressure in the LIGO gravitational-wave detector

We observed the effect of radiation pressure on the angular sensing and control system of the Laser Interferometer Gravitational-Wave Observatory (LIGO) interferometers core optics at LIGO Hanford Observatory. This is the first measurement of this effect in a complete gravitational-wave interferometer. Only one of the two angular modes survives with feedback control, because the other mode is suppressed when the control gain is sufficiently large. We developed a mathematical model to understand the physics of the system. This model matches well with the dynamics that we observe.