First Cross-Correlation Analysis of Interferometric and Resonant-Bar Gravitational-Wave Data for Stochastic Backgrounds

TL;DR

This study performed the first cross-correlation analysis between interferometric and resonant-bar gravitational-wave detectors to search for a stochastic background, setting a new upper limit that surpasses previous constraints.

Contribution

It introduces a novel cross-correlation method combining interferometric and resonant-bar data, improving sensitivity to stochastic gravitational-wave backgrounds.

Findings

No significant correlations detected.

Set a Bayesian 90% confidence upper limit of Omega_gw(f) <= 1.02.

Achieved a limit two orders of magnitude better than previous results.

Abstract

Data from the LIGO Livingston interferometer and the ALLEGRO resonant bar detector, taken during LIGO's fourth science run, were examined for cross-correlations indicative of a stochastic gravitational-wave background in the frequency range 850-950 Hz, with most of the sensitivity arising between 905 Hz and 925 Hz. ALLEGRO was operated in three different orientations during the experiment to modulate the relative sign of gravitational-wave and environmental correlations. No statistically significant correlations were seen in any of the orientations, and the results were used to set a Bayesian 90% confidence level upper limit of Omega_gw(f) <= 1.02, which corresponds to a gravitational wave strain at 915 Hz of 1.5e-23/rHz. In the traditional units of h_100^2 Omega_gw(f), this is a limit of 0.53, two orders of magnitude better than the previous direct limit at these frequencies. The method was also validated with successful extraction of simulated signals injected in hardware and software.