  We improve the effective-one-body (EOB) description of nonspinning coalescing
black hole binaries by incorporating several recent analytical advances,
notably: (i) logarithmic contributions to the conservative dynamics; (ii)
resummed horizon-absorption contribution to the orbital angular momentum loss;
and (iii) a specific radial component of the radiation reaction force implied
by consistency with the azimuthal one. We then complete this analytically
improved EOB model by comparing it to accurate numerical relativity (NR)
simulations performed by the Caltech-Cornell-CITA group for mass ratios
$q=(1,2,3,4,6)$. In particular, the comparison to NR data allows us to
determine with high-accuracy ($\sim 10^{-4}$) the value of the main EOB radial
potential: $A(u;\,\nu)$, where $u=GM/(R c^2)$ is the inter-body gravitational
potential and $\nu=q/(q+1)^2$ is the symmetric mass ratio. We introduce a new
technique for extracting from NR data an intrinsic measure of the phase
evolution, ($Q_\omega(\omega)$ diagnostics). Aligning the NR-completed EOB
quadrupolar waveform and the NR one at low frequencies, we find that they keep
agreeing (in phase and amplitude) within the NR uncertainties throughout the
evolution for all mass ratios considered. We also find good agreement for
several subdominant multipoles without having to introduce and tune any extra
parameters.
