Probability slice at ℓ = 4 for two different τ values, τ = 0.025 (top panels) and τ = 0.06 (bottom panels). The left panels show the signal-only distribution, while the right ones show the signal plus noise and systematic effects. For small τ values, the distribution is dominated by noise and systematic effects and is fitted poorly by the Hamimeche-Lewis-type model (red line), but is well-captured by the SimBaL polynomial approximation (blue curve).