Searching for stochastic gravitationalwave background with the colocated LIGO interferome.pdf

8 Searching for stochastic gravitational-wave 0 0 background with the co-located LIGO 2 n interferometers a J 2 Nickolas V Fotopoulos (for the LIGO Scientific Collaboration) 2 University of Wisconsin-Milwaukee, 1900 E Kenwood Blvd Rm 442, Milwaukee, WI, USA ] c E-mail: nvf@ q - r Abstract. g This paper presents techniques developed by the LIGO Scientic Collaboration to search for [ the stochastic gravitational-wave background using the co-located pair of LIGO interferometers 1 at Hanford, WA. We use correlations between interferometers and environment monitoring v instruments, as well as time-shifts between two interferometers (described here for the first 9 time) to identify correlated noise from non-gravitational sources. We veto particularly noisy 2 frequency bands and assess the level of residual non-gravitational coupling that exists in the 4 surviving data. 3 . 1 0 8 0 1. Introduction : v The LIGO (Laser Interferometer Gravitational-Wave Observatory) project has constructed i X two detectors, dubbed H1 and H2, at its Hanford observatory (on the US Department of r Energy’s Hanford Site in Washington, USA) and a third, L1, at its Livingston observatory (in a Livingston Parish, Louisiana, USA). These detectors are Fabry-Perot, power-recycled Michelson interferometers that detect minute changes in the differential lengths of their arms, the signatures of incident gravitational waves. The Fabry-Perot cavities, or arms, are 4 km long in the H1 and