feynlag.pheno.offshell.offshell_scalar_vv_width¶

feynlag.pheno.offshell.offshell_scalar_vv_width(m_S, m_V, width_V, coupling, backend='auto', n=400)[source]¶

Γ(S → V f f̄') for one fermion channel.

Analytic inner s₁₂ integral (scalar_vv_s12_integral()) then a 1-D numerical integral over s₂₃ = q² with the Breit–Wigner 1/((q²−m_V²)² + m_V²Γ_V²).

Parameters:

m_S – parent scalar mass (number).
m_V – vector mass (number).
width_V – the vector total width Γ_V (feeds the Breit–Wigner; below threshold, q² never reaches m_V² so this is negligible).
coupling – the product g_{SVV}² g_V² (number).
backend – "scipy", "gauss" (numpy) or "auto".
n – Gauss–Legendre node count for the 1-D integral.

Returns:

the partial width for one f f̄' channel (float). The caller multiplies by the open V^* fermion channels and (for S→VV*) the factor 2 for which V is on-shell.