The distribution of CP for different φ and φ _t . The upper panel denotes φ _t = 5/γ and φ varies from 10⁻⁴ to 10⁻¹. The bottom panel denotes φ _t = 1/γ and φ varies from 10⁻⁴ to 10⁻². We adopt below physical parameters: γ = 100, ω = ω _c , ρ = 10⁷ cm, Δθ _s = 10⁻³.