"Figure 12b" of "Search for new particles decaying into top quark-antiquark pairs in proton-proton collisions at $\sqrt{s}$ = 13 TeV"

Postfit distributions in $m_{t\bar{t}}$ in the single-lepton channel for data and simulation in the fourth bin of cos(theta*) in the t\bar{t} signal region, for the merged category, under the background-only hypothesis. The Z' boson signal with a relative width of 1% and a mass of 2 TeV is normalized to a cross section of 1 pb. The lower panels show the pulls, defined as $(\text{Data}-\text{Prediction})/\sigma$, where $\sigma$ denotes the total postfit uncertainty in each bin, relative to the SM prediction, defined as $\sigma^2 = \sigma_{\mathrm{data}}^2 - \sigma_{\mathrm{fit}}^2$.