We present two works which study global properties of EFT descriptions of physics beyond the Standard Model (BSM).
The first, based on arXiv:2008.08597, considers what BSM physics is amenable to a decoupling SMEFT description. The four scalar degrees of freedom of the Standard Model, the Higgs and the longitudinal components of the Ws and Z, can be viewed one of two ways: "SMEFT" wraps them up in a single Higgs doublet, whereas "HEFT" treats the Higgs and the Goldstones separately. We identify (field redefinition invariant) features of the scalar field space manifold that can only be described by the latter HEFT, and thereby identify two classes of UV completions for which HEFT is required: i) those which contain extra sources of electroweak symmetry breaking, ii) those which contain particles getting all of their mass from electroweak symmetry breaking.
The second, based on arXiv:2001.00017, considers weakly coupled heavy BSM physics that is amenable to a SMEFT description, and its generic pattern of tree-level and loop-level effects in observables. We do this in the high energy limit, where both the Standard Model and the BSM physics have a specific pattern of effects in helicity amplitudes. A main result is to extend non-interference theorems --- between SM and weakly coupled BSM physics in certain 2 -> 2 scattering processes --- to one-loop order.
|Collaboration / Activity||INFN Sezione di Trieste|
|First author||Dave Sutherland|