Abstract
Processes where W and Z bosons scatter into pairs of electroweak bosons W, Z, and Higgs, are sensitive probes of new physics in the electroweak sector. We study simplified models that describe typical scenarios of new physics and parameterize the range of possible LHC results between the standard-model prediction and unitarity limits. Extending the study beyond purely longitudinal scattering, we investigate the role of transversally polarized gauge bosons. Unitarity becomes an essential factor, and limits on parameters matched to the naive perturbative low-energy effective theory turn out to be necessarily model-dependent. We discuss the implications of our approach for the interpretation of LHC data on vector-boson scattering and Higgs-pair production.
Highlights
After the discovery of the Higgs boson [1,2], particle physics faces the question whether the new scalar sector is minimal or non-minimal, whether it is weakly or strongly interacting, and whether it validates or invalidates the accepted paradigm of quantum field theory as a universal description of particle interactions
Expectations for new physics beyond the standard model (SM) are constrained by available data
Numerical results of non-SM interactions of longitudinal scattering have clearly shown that for the level of deviations that can be detected by the LHC experiments, the unitarity limits are always violated in the high-energy range, if a naive SM effective theory (SMEFT) calculation is attempted
Summary
After the discovery of the Higgs boson [1,2], particle physics faces the question whether the new scalar sector is minimal or non-minimal, whether it is weakly or strongly interacting, and whether it validates or invalidates the accepted paradigm of quantum field theory as a universal description of particle interactions. 2 we discuss the structure of new interactions in the electroweak and Higgs sector, and state the underlying assumptions This defines the SMEFT ansatz, and it allows us to list the operators that describe the low-energy limit. We base the description of new effects beyond the SM on the following assumptions: (i) light fermions do not participate directly in new dynamics, (ii) the observed pattern of SM gauge invariance retains its relevance beyond the TeV range, and (iii) new degrees of freedom beyond the SM do not carry open color These assumptions are not mandatory but backed by the available precision data regarding flavor physics, QCD, new-physics searches at the LHC, and precision electroweak observables. SU (2)R-symmetric monomials are invariant under bi-unitary transformations of the form
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