Constant ALPHA_EM_MZ 

pub const ALPHA_EM_MZ: f64 = _; // 0.0078155529503712382f64

Running fine structure constant at Z pole: α(M_Z) ≈ 1/128

Due to vacuum polarization, α runs with energy scale Q:

α(Q) = α(0) / (1 - Δα(Q))
α(M_Z) ≈ 1/127.95

This is the correct value for precision electroweak calculations.