"End Matter Figure A (lower right)" 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 $\mathrm{X}\rightarrow\mathrm{ZY}\rightarrow\!2\mu 2\ell$ hypothesis, assuming $\mathcal{B}(\mathrm{Y}\rightarrow\!\mu\mu) = 1$, and $\mathrm{Z}$ decays to either $\mathrm{ee}$ or $\mu\mu$.