feynlag.pheno.amplitudes.vvs_squared¶

feynlag.pheno.amplitudes.vvs_squared(coupling, kin, m_v1=None, m_v2=None)[source]¶

S(P) → V(p₁) V(p₂) from a c·g^{μν} vertex (e.g. h W⁺W⁻).

With no spin average (scalar parent):

Σ|M|² = |c|² (−g_ab + p₁_a p₁_b/m₁²)(−g^{ab} + p₂^a p₂^b/m₂²)
      = |c|² [2 + (p₁·p₂)²/(m₁² m₂²)]