pub fn gamma_con(
epsilon: f64,
m_ev: f64,
cosmo: &Cosmology,
) -> Option<(f64, f64)>Expand description
NWA dark-photon conversion parameter γ_con (dimensionless).
γ_con = π ε² m² / (|d ln ω_pl²/d ln a|_{z_res} × T_γ(z_res) × H(z_res)),
following Chluba & Cyr (2024) Eq. 6. Returns None if no resonance exists
in the supported redshift range.
Returned tuple: (gamma_con, z_res).