Inelastic photon-neutrino interactions using an effective Lagrangian

We justify the feasibility of substituting a photon leg by a neutrino current in the Euler-Heisenberg Lagrangian to obtain an effective Lagrangian for the process gn→ggn and its crossed reactions. We establish the link between these processes and the four-photon scattering in both the standard model and the effective theory. As an application, we compute the processes gn→ggn and gg→gnn̄ , give their polarized cross sections, and show how to use the gg→gg results as a check. We settle the question about the disagreement between two computations in the literature concerning the reaction gg→gnn̄ . @S0556-2821~99!03301-9#