feynlag.pheno.vertices.resolve_leg¶

feynlag.pheno.vertices.resolve_leg(leg, particle_map)[source]¶

Map a Weyl leg to its physical particle, falling back to the leg.

A Dirac fermion is modelled in feynlag as two WeylFermion`s (see ``CLAUDE.md`: DiracFermion raises on construction), so e_L and e_R are different legs even though Z → e⁺e⁻ is one channel fed by both. particle_map is how the caller states that identification: {eL[i]: e, eR[i]: e, eLbar[i]: ebar, ...}. Without it the left- and right-handed currents would be counted as two separate decays, each missing the other’s interference with the mass terms.

Lookup falls back to the leg’s IndexedBase so a flavour-indexed leg can be mapped once for all generations.