  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.
