"Figure 2 (left)" of "Search for heavy resonances decaying into four-lepton final states via light bosons in proton-proton collisions at $\sqrt{s}$ = 13 TeV"

The observed and expected limit on the cross section times branching fraction and observed local significance as a function of $M_{\mathrm{X}}$ and $M_{\mathrm{Y}}$ for $\mathrm{X}\rightarrow\mathrm{YY}\rightarrow\!4\ell$ hypothesis, assuming $\mathcal{B}(\mathrm{Y}\rightarrow\!\mathrm{ee}) = \mathcal{B}(\mathrm{Y}\rightarrow\!\mu\mu) = 0.5$.