  Understanding the collisional behavior of dust aggregates is essential in the
context of planet formation. It is known that low-velocity collisions of dust
aggregates result in bouncing rather than sticking when the filling factor of
colliding dust aggregates is higher than a threshold value. However, a large
discrepancy between numerical and experimental results on the threshold filling
factor was reported so far. In this study, we perform numerical simulations
using soft-sphere discrete element methods and demonstrate that the sticking
probability decreases with increasing aggregates radius. Our results suggest
that the large discrepancy in the threshold filling factor may reflect the
difference in the size of dust aggregates in earlier numerical simulations and
laboratory experiments.
