Fig. 2.

Distributions of (left) dijet mass $m_{jj}$, (middle) three-jet mass $m_{jjj}$, and (right) ratio of three-jet mass to dijet mass $R_{3/2}$, measured in data and compared to expectations after applying all analysis event selection criteria (i.e. for region $F$). The shape and normalisation of the multijet background distributions (green shaded histograms) are calculated using Eq. (4). The distributions for the $t\overline{t}$ events (white histograms) are taken from the MC simulation using a top-quark mass value of $172.5\mathrm{GeV}$. The insets under the distributions show the ratio of data to the summed contributions of $t\overline{t}$ MC signal and modelled multijet background (see Sect. 4). The error bars represent the statistical uncertainties on the data. The shaded bands show the statistical and systematic (see Sect. 6) uncertainty on the expected signal and background distributions