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4.Conservation of energy and momentum.For each vertex, write a delta function ofthe form(2π)2
5.Integration over internal momenta.For each internal line, write down a factor1(2π)4d4qj(4)and integrate over all internal momenta.6.Cancel the delta function.The result will include a delta function(2π)4δ4(p1+p2+· · ·+pn)(5)enforcing overall conservation of energy and momentum. Erase this factor, and whatremains is-iM.17 — Lifetime of Higgs particleBecause of its role in giving mass to fermions, the (still-hypothetical-but-most-likely-soon-to-be-discovered) Higgs scalar couples to each fermion with a strengthmf(GF√2)1/2, withm