"Figure 10a" of "Search for ttbar resonances in final states with exactly one or two leptons using 140 fb$^{-1}$ of pp collision data at $\sqrt{s}=13$ TeV with the ATLAS experiment"

Observed (pink data points) and expected (black dashed line) upper limits on the signal cross-section times branching ratio to tt̄ for the (a) Z', (b) GKK, and (c) gKK signals at 95% CL. Approximate limits for intermediate masses are interpolated between the tested mass hypotheses. For the GKK signal in (b), the detector resolution is finer than the grid spacing, so the interpolation is only for display purposes. The theory predictions for the production cross-section times branching ratio at the corresponding masses are also shown in (a) for a Z' with a width of 3% (blue line) and a Z' with a width of 1.2% (dark red line), in (b) a GKK with a width ranging from 3%–6%, and in (c) a gKK with a width of 30%. Also shown is the relative contribution of the 1-lepton (red dashed and dotted line) and 2-lepton (purple long-dashed and dotted line) channels to the expected combination limits.