L. Merlo

Disentangling a dynamical Higgs

A bstractThe pattern of deviations from Standard Model predictions and couplings is different for theories of new physics based on a non-linear realization of the SU(2)L × U(1)Y gauge symmetry breaking and those assuming a linear realization. We clarify this issue in a model-independent way via its effective Lagrangian formulation in the presence of a light Higgs particle, up to first order in the expansions: dimension-six operators for the linear expansion and four derivatives for the non-linear one. Complete sets of gauge and gauge-Higgs operators are considered, implementing the renormalization procedure and deriving the Feynman rules for the non-linear expansion. We establish the theoretical relation and the differences in physics impact between the two expansions. Promising discriminating signals include the decorrelation in the non-linear case of signals correlated in the linear one: some pure gauge versus gauge-Higgs couplings and also between couplings with the same number of Higgs legs. Furthermore, anomalous signals expected at first order in the non-linear realization may appear only at higher orders of the linear one, and vice versa. We analyze in detail the impact of both type of discriminating signals on LHC physics.

Analysis of general power counting rules in effective field theory

We derive the general counting rules for a quantum effective field theory (EFT) in

The complete HEFT Lagrangian after the LHC Run I

mathsf {d}

Sigma decomposition: the CP-odd Lagrangian

d dimensions. The rules are valid for strongly and weakly coupled theories, and they predict that all kinetic energy terms are canonically normalized. They determine the energy dependence of scattering cross sections in the range of validity of the EFT expansion. We show that the size of the cross sections is controlled by the

Non-linear Higgs portal to Dark Matter

Lambda

Baryon non-invariant couplings in Higgs effective field theory

Λ power counting of EFT, not by chiral counting, even for chiral perturbation theory (