Towards the Ultimate SM Fit to Close in on Higgs Physics

TL;DR

The paper develops a model-independent SMEFT framework to quantify how beyond-Standard-Model effects could appear in Higgs and electroweak physics. By organizing dimension-6 operators into groups tied to distinct experimental constraints and performing a global EW fit, the authors map which Wilson coefficients are tightly restricted and which directions remain open. They show that, with current data, most Higgs-related deformations are already constrained by EW observables and TGC measurements, except for potential large deviations in BR$(h o Z extgamma)$; future LHC measurements of TGC could further tighten these bounds. The analysis provides a road map for interpreting future Higgs measurements in a unified EFT framework and for identifying the most sensitive experimental probes of BSM effects. $ $

Abstract

With the discovery of the Higgs at the LHC, experiments have finally addressed all aspects of the Standard Model (SM). At this stage, it is important to understand which windows for beyond the SM (BSM) physics are still open, and which are instead tightly closed. We address this question by parametrizing BSM effects with dimension-six operators and performing a global fit to the SM. We separate operators into different groups constrained at different levels, and provide independent bounds on their Wilson coefficients taking into account only the relevant experiments. Our analysis allows to assert in a model-independent way where BSM effects can appear in Higgs physics. In particular, we show that deviations from the SM in the differential distributions of h->Vff are related to other observables, such as triple gauge-boson couplings, and are then already constrained by present data. On the contrary, BR(h-> Z+gamma) can still hide large deviations from the SM.