Stars in globular clusters can act either as sources for MACHOs (Massive
Astrophysical Compact Halo Objects) located along the line of sight or as
lenses for more distant background stars. Although the expected rate of
microlensing events is small, such observations can lead to very useful
results. In particular, one could get information on the shape of the galactic
halo along different lines of sight, allowing to better constrain its total
dark matter content. Moreover, on can also infer the total dark matter content
of globular clusters, which is presently not well known. To this latter
purpose, we analyse the microlensing events towards the galactic bulge, which
lie close to the three globular clusters NGC 6522, NGC 6528 and NGC 6540. We
find evidence that some microlensing events are indeed due to MACHOs located in
the globular clusters, suggesting, therefore, that these clusters contain a
significant amount of dark matter.Comment: 15 pages, 10 figures included. Accepted for publication in A &
