Modulating the experimental signature of a stochastic gravitational wave background - art. no. 082002

Detecting a stationary, stochastic gravitational wave signal is complicated by the impossibility of observing the detector noise independently of the signal. One consequence is that we require at least two detectors to observ e the signal, which will be apparent in the cross-correlation of the detect or outputs. A corollary is that there remains a systematic error, associate d with the possible presence of correlated instrumental noise, in any obser vation aimed at estimating or limiting a stochastic gravitational wave sign al. Here we describe a method of identifying this systematic error by varyi ng the orientation of one of the detectors, leading to separate and indepen dent modulations of the signal and noise contribution to the cross-correlat ion. Our method can be applied to measurements of a stochastic gravitationa l wave background by the ALLEGRO-LIGO Livingston Observatory detector pair. We explore-in the context of this detector pair-how this new measurement t echnique is insensitive to a cross-correlated detector noise component that can confound a conventional measurement.