(color online) Mean square displacement of the center of mass of system for different angular velocities with an area fraction of ρ=0.1. Here l = 3, n_B=4, and γ= π/2. Solid red lines are fitting curves based on Eq. (7) with the parameter of , A=1.40 for ω=0 (black symbols), , for ω=0.5 (pink symbols), and , for ω=1.0 (blue symbols). (b) The enlarged figure of the front part of (a) shows that the oscillation period of the curve is consistent with the rotation period of chiral active particles, and the amplitude of oscillation decreases gradually with time t.