Multi-photon Decays of the Higgs Boson in Standard Model: Leading Terms from Heisenberg-Euler Effective Lagrangian

We calculate the multi-photon decay widths of the Higgs boson from an effective Lagrangian for a system of electromagnetic and Higgs fields. We utilize a low-energy theorem to connect the above Lagrangian to the Heisenberg-Euler effective Lagrangian induced by charged particles that gain mass from interactions with the Higgs boson. In the standard model only the W^\pm gauge bosons and the top quark are relevant, and we compute their contributions to the effective couplings and the multi-photon decay widths of the Higgs boson.