4 Four-fermion decay modes 9 17 4.1 h→ 4 f neutral currents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 18 4.2 h→ 4 f charged currents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 19 4.3 h→ 4 f complete decomposition . . . . . . . . . . . . . . . . . . . . . . . . . 11 20 4.4 Physical PO for h→ 4` . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 21 4.5 Physical PO for h→ 2`2ν . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 22

We discuss the conditions for an effective field theory (EFT) to give an adequate low11 energy description of the underlying physics beyond the Standard Model (SM). Starting 12 from the EFT where the SM is extended by dimension-6 operators, experimental data can 13 be used without further assumptions to measure (or set limits on) the EFT parameters. 14 The interpretation of these results requires instead a set of broad assumptions on the UV 15 dynamics. This allows one to establish, in a bottom-up approach, the validity range of 16 the EFT description, and to assess the error associated with the truncation of the EFT 17 series. We give a practical prescription on how experimental results should be reported, 18 so that they admit a maximally broad range of theoretical interpretations. Namely, the 19 experimental constraints on dimension-6 operators should be reported as functions of the 20 kinematic variables that set the relevant energy scale of the studied process. This is especially 21 important for hadron collider experiments where collisions probe a wide range of energy scales. 22

We present a combined analysis of LHC Higgs data (signal strengths) together with LEP-2 WW production measurements. To characterize possible deviations from the standard model (SM) predictions, we employ the framework of an effective field theory (EFT) where the SM is extended by higher-dimensional operators suppressed by the mass scale of new physics Λ. The analysis is performed consistently at the order Λ(-2) in the EFT expansion keeping all the relevant operators. While the two data sets suffer from flat directions, together they impose stringent model-independent constraints on the anomalous triple gauge couplings.