Global fit to Higgs signal strengths and couplings and implications for extended Higgs sectors

Abstract

The most recent LHC data have provided a considerable improvement in the precision with which various Higgs production and decay channels have been measured. Using all available public results from ATLAS, CMS and the Tevatron, we derive for each final state the combined confidence level contours for the signal strengths in the (gluon fusion + ttH associated production) versus (vector boson fusion + VH associated production) space. These "combined signal strength ellipses" can be used in a simple, generic way to constrain a very wide class of New Physics models in which the couplings of the Higgs boson deviate from the Standard Model prediction. Here, we use them to constrain the reduced couplings of the Higgs boson to up-quarks, down-quarks/leptons and vector boson pairs. We also consider New Physics contributions to the loop-induced gluon-gluon and photon-photon couplings of the Higgs, as well as invisible/unseen decays. Finally, we apply our fits to some simple models with an extended Higgs sector, in particular to Two-Higgs-Doublet models of Type I and Type II, the Inert Doublet model, and the Georgi-Machacek triplet Higgs model.

Figures (15)

• Figure 1: Combined signal strength ellipses for the $\gamma\gamma$, $VV=ZZ,WW$ and $b\bar{b}=\tau\tau$ channels. The filled red, orange and yellow ellipses show the 68%, 95% and 99.7% CL regions, respectively, derived by combining the ATLAS, CMS and Tevatron results. The red, orange and yellow line contours in the right-most plot show how these ellipses change when neglecting the Tevatron results. The white stars mark the best-fit points.
• Figure 2: Combined signal strength ellipses as in Fig. \ref{['fig:ellipses1']} but treating the couplings to $b\bar{b}$ and $\tau\tau$ separately.
• Figure 3: $\Delta \chi^2$ distributions in 1D and 2D for the fit of $\Delta C_g$ and $\Delta C_\gamma$ for $C_U=C_D=C_V=1$. In the 1D plots, the solid (dashed) lines are for the case that invisible/unseen decays are absent (allowed). In the 2D plot, the red, orange and yellow areas are the 68%, 95% and 99.7% CL regions, respectively, assuming invisible decays are absent. The white star marks the best-fit point. The black and grey lines show the 68% and 95% CL contours when allowing for invisible decays.
• Figure 4: Fit of $C_U$, $C_D$, $C_V$ for $\Delta C_g=\Delta C_\gamma=0$. The plots show the 1D $\Delta\chi^2$ distribution as a function of $C_U$ (left) and $C_V$ (right). The solid (dashed) lines are for the case that invisible/unseen decays are absent (allowed).
• Figure 5: Fit of $C_U>0$, $C_D>0$ and $C_V$ for $\Delta C_g=\Delta C_\gamma=0$. The red, orange and yellow areas are the 68%, 95% and 99.7% CL regions, respectively, assuming invisible decays are absent. The white star marks the best-fit point.