  We have monitored a sample of 27 nearby globular clusters in the hard X-ray
band (20-120 keV) for approximately 1400 days using the BATSE instrument on
board the Compton Gamma-Ray Observatory. Globular clusters may contain a large
number of compact objects (e.g., pulsars or X-ray binaries containing neutron
stars) which can produce hard X-ray emission. Our search provides a sensitive
(~50 mCrab) monitor for hard X-ray transient events on time scales of >1 day
and a means for observing persistent hard X-ray emission. We have discovered no
transient events from any of the clusters and no persistent emission. Our
observations include a sensitive search of four nearby clusters containing dim
X-ray sources: 47 Tucanae, NGC 5139, NGC 6397, and NGC 6752. The non-detection
in these clusters implies a lower limit for the recurrence time of transients
of 2 to 6 years for events with luminosities >10^36 erg s^-1 (20-120 keV) and
~20 years if the sources in these clusters are taken collectively. This
suggests that the dim X-ray sources in these clusters are not transients
similar to Aql~X-1. We also place upper limits on the persistent emission in
the range 2-10*10^34 erg s^-1 (2 sigma, 20-120 keV) for these four clusters.
For 47 Tuc the upper limit is more sensitive than previous measurements by a
factor of 3. We find a model dependent upper limit of 19 isolated millisecond
pulsars (MSPs) producing gamma-rays in 47 Tuc, compared to the 11 observed
radio MSPs in this cluster.
