"Figure 18 [Combined Expected]" of "Combination of ATLAS and CMS searches for Higgs boson pair production at $\sqrt{s} = 13$ TeV"

Expected value of the simultaneous scan of the profile likelihood test statistic ($-2\ ln\ \Lambda$) as a function of the individual signal strengths for the ggF $\mu_{HH}^{ggF}$ and VBF $\mu_{HH}^{VBF}$ HH production modes for the combination of ATLAS and CMS. All Higgs boson couplings are fixed to their SM predictions. The likelihood function is not well defined in regions with large negative values of either $\mu_{HH}^{ggF}$ or $\mu_{HH}^{VBF}$, where the total prediction for the sum of signal and backgrounds can become negative in some categories of the input analyses. This region is therefore not shown.