  Recent simulations have shown that the formation of planets in circumbinary
configurations (such as those recently discovered by Kepler) is dramatically
hindered at the planetesimal accretion stage. The combined action of the binary
and the protoplanetary disk acts to raise impact velocities between km-sized
planetesimals beyond their destruction threshold, halting planet formation
within at least 10 AU from the binary. It has been proposed that a primordial
population of "large" planetesimals (100 km or more in size), as produced by
turbulent concentration mechanisms, would be able to bypass this bottleneck;
however, it is not clear whether these processes are viable in the highly
perturbed circumbinary environments. We perform two-dimensional hydrodynamical
and N-body simulations to show that km-sized planetesimals and collisional
debris can drift and be trapped in a belt close to the central binary. Within
this belt, planetesimals could initially grow by accreting debris, ultimately
becoming "indestructible" seeds that can accrete other planetesimals in-situ
despite the large impact speeds. We find that large, indestructible
planetesimals can be formed close to the central binary within $10^5$ years,
therefore showing that even a primordial population of "small" planetesimals
can feasibly form a planet.
