  We present an indirect dynamical evidence, based on the measure of the core
to half mass radius ratio (rc/rh), that a significant fraction of globular
clusters in our galaxy with an age greater than 10 half-mass relaxation times
(t_rh) host an intermediate mass black hole (IMBH). In fact, after a few t_rh
much of the memory about the details of initial conditions is erased and rc/rh
is determined solely by the balance of the stellar encounters energy production
in the core with the dissipation due to global expansion of the cluster. Here
we compare the observed values of rc/rh from a sample of 57 galactic globular
cluster, selected to be dynamically old and not strongly influenced by tidal
forces, with the theoretical expectation for the rc/rh ratio based on
analytical models and detailed numerical simulations. The simulations of the
evolution of star clusters considered include combinations of single stars,
primordial binaries and IMBH. For at least half of the clusters in our sample
the observed rc/rh ratio appears to be too large to be explained without
invoking the presence of an IMBH at the center of the system.
