Differential mass distribution from one of the simulations with r₀ = 10 au and δ = 10⁻⁵ at t₀ + 5 × 10⁴ yr (top), t₀ + 2 × 10⁵ yr (middle), and t₀ + 3.7 × 10⁵ yr (bottom) with ten mass bins in each decade. The red line in each panel shows the corresponding estimation of the pebble accretion timescale τ_PA with respect to mass for the instantaneous e_rms of all bodies. The grey histogram in the bottom panel shows the initial mass of all planetesimals produced throughout the simulation. The evolution shows a window period exists where significant growth by pebble accretion is possible. This period starts from the time of the formation of the first planetesimal with m > M_PA,hw and ends at the time when it becomes massive enough to excite the less massive bodies to high eccentricity in a short timescale.