Speaker
Description
Particle production at LHC energies involves perturbative (hard) and non-perturbative (soft) QCD regimes. The charged-particle multiplicity cannot be calculated using purely perturbative methods and is generally described by phenomenological models. In this contribution, we report on soft QCD variables, such as inelastic, single, double and central diffractive cross-sections, charged-particle multiplicities and observables characterizing the Underlying Event. Results are presented for all collision systems (pp, p-Pb, Pb-Pb and Xe-Xe) and for all centre of mass energies from $\sqrt{s}$ = 0.9 to 13 TeV and $\sqrt{s_\mathrm{NN}}$ = 2.76 to 8.16 TeV. This covers a large range of energy, system and multiplicities with new results recently measured by ALICE in pp high multiplicity, p-Pb and Xe-Xe events at the LHC. Finally, we investigate the evolution of particle production with energy and system size and compare to models based on various particle production mechanisms and different initial conditions, summarizing the understanding of soft QCD 8 years after the start of data taking at the LHC.
