Towards the first search for a stochastic background in LIGO data: applications of signal simulations

We describe the utility of simulated-signal injection studies on earth-based gravitational-wave (GW) interferometric data toward obtaining bounds on the strength of a stochastic GW background. The existence of such a background today is predicted by several cosmological models, but with varying strengths and power spectra. Earth-based detectors, such as LIGO, will eventually achieve enough sensitivity to start constraining some of these models through these bounds. A significant part of the effort to use LIGO data to place such bounds is to estimate the efficiency of the data analysis pipeline in detecting the variety of predicted backgrounds. We took the data taking opportunity offered by the first science run at LIGO to inject simulated signals of varying strengths both in hardware as well as software. We describe here the results obtained in searching for these injection backgrounds. We discuss especially those results that either varied from the expected ones or are crucial to the search for a stochastic GW background. The reasons behind the variations are also explained.