The Higgs Legacy of the LHC Run I

TL;DR

This work presents a comprehensive Run I Higgs analysis using the SFitter framework, comparing traditional Higgs-coupling fits with a linear dimension-6 EFT including kinematic distributions and off-shell information. It demonstrates overall SM compatibility, tightens constraints on invisible decays (BR$_{inv}$ around 0.16), and introduces a nine-operator EFT basis to map Higgs interactions to measurable channels. Incorporating differential distributions reduces degeneracies and probes higher-energy scales around $\Lambda \sim 300$–$500$ GeV, while off-shell measurements enhance sensitivity to the Higgs width and momentum-dependent couplings, yielding a width bound of $\Gamma_H < 9.3\,\Gamma_H^{SM}$ at 68% CL. The results underscore the complementary roles of rate and kinematic information and highlight theoretical-uncertainty considerations that will guide Run II analyses and EFT validity checks.

Abstract

Based on Run I data we present a comprehensive analysis of Higgs couplings. For the first time this SFitter analysis includes independent tests of the Higgs-gluon and top Yukawa couplings, Higgs decays to invisible particles, and off-shell Higgs measurements. The observed Higgs boson is fully consistent with the Standard Model, both in terms of coupling modifications and effective field theory. Based only on Higgs total rates the results using both approaches are essentially equivalent, with the exception of strong correlations in the parameter space induced by effective operators. These correlations can be controlled through additional experimental input, namely kinematic distributions. Including kinematic distributions the typical Run I reach for weakly interacting new physics now reaches 300 to 500 GeV.

Figures (15)

• Figure 1: 68% CL error bars on the deviations $\Delta_x$ from all Standard Model couplings of the observed Higgs boson. In this fit we do not allow for new particles in the effective Higgs couplings to photons and gluons, $\Delta_\gamma = 0 = \Delta_g$. The results labelled 'SM exp' assume central values on the Standard Model expectation, but the current data error bars.
• Figure 2: 68% CL error bars on the deviations $\Delta_x$ from all Standard Model couplings of the observed Higgs boson. For the loop-induced couplings we allow new contributions to the $H\gamma\gamma$ coupling only ($\Delta_g=0$, left) and to the $H\gamma\gamma$ and $Hgg$ couplings (right). The results labelled 'SM exp' assume central values on the Standard Model expectation, but the current data error bars.
• Figure 3: Correlations between different coupling modifications for the fit including $\Delta_\gamma$ as well as $\Delta_g$. The 1-dimensional profile likelihoods correspond to the results shown as the blue bars in the right panel of Fig. \ref{['fig:delta_g']}.
• Figure 4: 68% CL error bars on the deviations $\Delta_x$ from all Standard Model couplings of the observed Higgs boson. In addition to all couplings predicted by the Standard Model we include a Higgs decay to invisible particles. The results labelled 'SM exp' assume central values on the Standard Model expectation, but the current data error bars.
• Figure 5: Correlations between different coupling modifications to SM particles and the invisible branching ratio. The corresponding 1-dimensional profile likelihoods are shown as the blue bars in Fig. \ref{['fig:delta_gi']}.