feynlag.pheno.kinematics.two_body_phase_space

feynlag.pheno.kinematics.two_body_phase_space(M_parent, m1, m2)

Two-body phase space integration factor.

Γ = ⟨|M|²⟩ × √λ(M², m₁², m₂²)/(16 π M³) for a spin-averaged ⟨|M|²⟩ — i.e. everything in Γ except the amplitude.

Parameters:

• M_parent – Mass of the decaying particle.

• m1 – Mass of first daughter.

• m2 – Mass of second daughter.

Returns:

The kinematic factor integrated over phase space.