Updated Global Analysis of Higgs Couplings

TL;DR

The paper performs a global analysis of Higgs couplings using LHC and Tevatron data up to Moriond 2013 to test whether the 126 GeV boson behaves like the Standard Model Higgs. It employs two complementary parameterizations of couplings: (a,c) for tree-level couplings and a mass-scaling (M,ε) to probe linearity in masses, along with loop factors $c_g$ and $c_\gamma$. The results show SM-like couplings within a few percent, a preference for same-sign boson/fermion couplings, a mass dependence linear in mass with $M\approx v$, and tight constraints on invisible decays. Composite-Higgs scenarios are increasingly constrained, while supersymmetry remains compatible. The work provides a framework for updating Higgs coupling fits as more data accumulate.

Abstract

There are many indirect and direct experimental indications that the new particle H discovered by the ATLAS and CMS Collaborations has spin zero and (mostly) positive parity, and that its couplings to other particles are correlated with their masses. Beyond any reasonable doubt, it is a Higgs boson, and here we examine the extent to which its couplings resemble those of the single Higgs boson of the Standard Model. Our global analysis of its couplings to fermions and massive bosons determines that they have the same relative sign as in the Standard Model. We also show directly that these couplings are highly consistent with a dependence on particle masses that is linear to within a few %, and scaled by the conventional electroweak symmetry-breaking scale to within 10%. We also give constraints on loop-induced couplings, on the total Higgs decay width, and on possible invisible decays of the Higgs boson under various assumptions.

Figures (10)

• Figure 1: A compilation of the Higgs signal strengths measured by the ATLAS, CDF, D0 and CMS Collaborations in the ${\bar{b}} b$, $\tau^+ \tau^-$, $\gamma \gamma$, $WW^*$ and $ZZ^*$ final states. We display the combinations of the different channels for each final state, and also the combination of all these measurements, with the result for the VBF and VH channels (excluding the $\gamma\gamma$ final state) shown separately in the bottom line.
• Figure 2: The constraints in the $(a, c)$ plane imposed by the measurements in Fig. \ref{['fig:mulist']} in the ${\bar{b}} b$ final state (top left), in the $\tau^+ \tau^-$ final state (top right), in the $\gamma \gamma$ final state (middle left), in the $WW^*$ final state (middle right) and in the $ZZ^*$ final state (bottom left). The combination of all these constraints is shown in the bottom right panel.
• Figure 3: The one-dimensional likelihood functions for the boson coupling parameter $a$ (left panel) and the fermion coupling parameter $c$ (right panel), as obtained by marginalizing over the other parameter in the bottom right panel of Fig. \ref{['fig:ac']}.
• Figure 4: Left: The constraints in the $(c_\gamma, c_g)$ plane imposed by the measurements in Fig. \ref{['fig:mulist']}, assuming the Standard Model values for the tree-level couplings to massive bosons and fermions, i.e., $a = c = 1$. Right: The constraints in the $(a, c)$ plane when marginalizing over $c_\gamma$ and $c_g$.
• Figure 5: The one-dimensional likelihood functions for $c_\gamma$ (left panel) and $c_g$ (right panel), as obtained by marginalizing over the other variable in the bottom right panel of Fig. \ref{['fig:cgammacg']}, assuming the Standard Model values for the tree-level couplings to massive bosons and fermions.