Abstract
We perform a comprehensive study of the Higgs couplings, gauge-boson couplings to fermions and triple gauge boson vertices. We work in the framework of effective theories including the effects of the dimension-six operators contributing to these observables. We determine the presently allowed range for the coefficients of these operators via a 20 parameter global fit to the electroweak precision data, as well as electroweak diboson and Higgs production data from LHC Run 1 and 2. We quantify the improvement on the determination of the 20 Wilson coefficients by the inclusion of the Run 2 results. In particular we present a novel analysis of the ATLAS Run 2 36.1 $\rm fb^{-1}$ data on the transverse mass distribution of $W^+W^-$ and $W^\pm Z$ in the leptonic channel which allow for stronger tests of the triple gauge boson vertices. We discuss the discrete (quasi)-degeneracies existing in the parameter space of operator coefficients relevant for the Higgs couplings to fermions and gauge bosons. In particular we show how the inclusion of the incipient $tH$ data can break those degeneracies in the determination of the top-Higgs coupling. We also discuss and quantify the effect of keeping the terms quadratic in the Wilson coefficients in the analysis and we show the importance of the Higgs data to constrain some of the operators that modify the triple gauge boson couplings in the linear regime.
Highlights
Since the discovery of a new state resembling the SM Higgs boson [1,2], the CERN Large Hadron Collider (LHC) has accumulated an impressive amount of data that allow new searches for extensions of the Standard Model (SM), as well as detailed studies of the SM predictions
We follow this road by performing a comprehensive analysis of the observables related to the electroweak sector, which at present allows for precision tests of the couplings between electroweak gauge bosons and fermions, triple electroweak gauge couplings (TGC), and the couplings of the Higgs to fermions and gauge bosons
In order to obtain the bounds on the Wilson coefficients in the effective Lagrangian in Eq (2.15), we study the WþW− and WÆZ productions in the leptonic channel using the available kinematic distribution that is most sensitive for TGC analysis
Summary
Since the discovery of a new state resembling the SM Higgs boson [1,2], the CERN Large Hadron Collider (LHC) has accumulated an impressive amount of data that allow new searches for extensions of the Standard Model (SM), as well as detailed studies of the SM predictions. The effective Lagrangian approach [3,4,5] is a modelindependent framework, which, using as inputs the low energy particle contents and symmetries, describes new physics that is expected to manifest itself directly at an energy scale Λ larger than the scale at which the experiments are performed, by including in the Lagrangian higherdimension operators In this context, and within the present experimental results, we proceed by assuming that the observed scalar belongs to a light electroweak doublet and that the SUð2ÞL ⊗ Uð1ÞY symmetry is linearly realized in the effective theory. In the framework of the effective Lagrangian described above ( recently labeled in the literature as the SMEFT), our study involves 20 dimension-six operators whose coefficients are determined by means of a global fit to the relevant data, including low-energy electroweak precision measurements as well as LHC data on gauge boson pair production and Higgs observables.
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