Imprint of the merger and ring-down on the gravitational wave background
  from black hole binaries coalescence
  We compute the gravitational wave background (GWB) generated by a
cosmological population of (BH-BH) binaries using hybrid waveforms recently
produced by numerical simulations of (BH-BH) coalescence, which include the
inspiral, merger and ring-down contributions. A large sample of binary systems
is simulated using the population synthesis code SeBa, and we extract
fundamental statistical information on (BH-BH) physical parameters (primary and
secondary BH masses, orbital separations and eccentricities, formation and
merger timescales). We then derive the binary birth and merger rates using the
theoretical cosmic star formation history obtained from a numerical study which
reproduces the available observational data at redshifts $z < 8$. We evaluate
the contributions of the inspiral, merger and ring-down signals to the GWB, and
discuss how these depend on the parameters which critically affect the number
of coalescing (BH-BH) systems. We find that Advanced LIGO/Virgo have a chance
to detect the GWB signal from the inspiral phase with a $(S/N)=10$ only for the
most optimistic model, which predicts the highest local merger rate of 0.85
Mpc$^{-3}$ Myr$^{-1}$. Third generation detectors, such as ET, could reveal the
GWB from the inspiral phase predicted by any of the considered models. In
addition, ET could sample the merger phase of the evolution at least for models
which predict local merger rates between $[0.053 - 0.85]$ Mpc$^{-3}$
Myr$^{-1}$, which are more than a factor 2 lower the the upper limit inferred
from the analysis of the LIGO S5 run\cite{Abadieetal2011}.
