LIGO Detector Characterization for the Fourth Observing Run

The LIGO detectors identified over 75 significant gravitational wave detection candidates during the first half of their fourth observing run, nearly doubling the total number of gravitational waves seen in the preceding observing campaign. In this poster we describe some of the detector characterization and data quality investigations which took place between the end of the third and the end of the first half of the fourth LIGO observing run. These studies have identified and eliminated noise sources at the detectors, produced new, more sophisticated methods to rapidly vet gravitational wave detection candidates and produced essential data products for searches for gravitational waves from known and novel sources. In addition to these contributions to searches for gravitational wave transients, continued data quality work has led to the identification and mitigation of long-lived spectral artifacts in the LIGO detector data, improving LIGO's searches for continuous-wave sources and the stochastic gravitational wave background.