Speaker
Description
A correct modelling of the underlying event in proton-proton collisions is important for the proper simulation of kinematic distributions of high-energy collisions. The ATLAS collaboration extended previous studies at 7 TeV with a leading track or jet or Z boson by a new study at 13 TeV, measuring the number and transverse-momentum sum of charged particles as a function of pseudorapidity and azimuthal angle in dependence of the reconstructed leading track. These measurements are sensitive to the underlying-event as well as the onset of hard emissions. The results are compared to predictions of several MC generators. A similar comparison between measurements and MC generator predictions will be shown, if available, for the strange meson content in top-quark pair events.
Studies of particle correlations in high-energy collisions can provide valuable insights into the detailed understanding of the space-time geometry of the hadronization region. The ATLAS collaboration has studied the momentum difference between pairs of charged particles in data collected at center-of-mass energies of 0.9TeV and 7TeV in view of the presence of Bose-Einstein interference or new models of string fragmentation.