Fig. 10.

The distributions of the sum of the squared transverse momentum for tracks from primary vertices, shown for simulated hard-scatter processes and a minimum-bias sample. In the case of the $Z\to \mathit{\mu }\mathit{\mu }$ process, only events with at least two muons with $p_{\text{T}}>15$ GeV reconstructed within the ATLAS inner detector acceptance are shown. The $t\overline{t}$ process is filtered to select decays with leptons. The distributions are normalised to the same area