EFT amplitudes via on-shell methods

 

Abstract

 

We use on shell methods to compute EFT scattering amplitudes, both  massless and massive, with no reference to a Lagrangian. On shell methods avoid the usual complications that accompany an amplitude computation a la Feynman. Lorentz symmetry, global symmetry, Bose statistics and unitarity (almost) completely fix the allowed kinematical structures. We will demonstrate this approach by calculating several amplitudes completely "bottom-up", i.e., with unitarity and only the known symmetries and particles to guide us. Applying on-shell methods to an electroweak-like sector of the Standard Model, we demonstrate how relations between masses and couplings, which are the result of the Higgs mechanism, now emerge by imposing unitarity.